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Pelican Parts Technical Articles Main Image

Mercedes-Benz SLK 230 K40 Overload Protection Relay Repair

Applicable Models:

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Rennline Performance Products Lifetime Replacement Parts Pelican Parts Tech Forums
  • Parts Required: Hopefully none
  • Performance Gain: Restored engine firing and smooth running
  • Complementary Modification: Check the fan below the K40 and repair and replace if necessary

The notorious K40 overload protection unit is a well-known cause of starting, idling, and engine stumbling problems.

This unit provides voltage to the control modules and electrical components, including the fuel pump, electric air pump, and horn. When the K40 malfunctions, these components don't get their required voltage.

Troubleshooting should obviously begin with any diagnostic trouble codes (DTCs), followed by checking for blown fuses. If those lead to dead-ends, the K40 is worth scrutinizing.

The K40 relay is located in the control module box, under the hood. In left-hand-drive R170 SLKs, this box is near the exhaust manifold. A heat shield and a blower motor keep the electronics in the box cool. A non-functioning blower can be a root cause. With the ignition switched on, this fan is audible, and airflow should be felt with the control module's cover removed.

Visual inspection of the K40 might reveal a correctable flaw. Spending a few minutes under the hood can save more than $100 by not having to replace the unit. And if the K40 is bad, at least you now know how to replace it yourself.

Hot tip

Use electrical contact cleaner on the plug terminals

Wayne R. Dempsey, Co-Founder & DIY Expert

Tom Morr, DIY Expert

//

Project Photos

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Figure 1 Always disconnect the ground strap on the battery before doing any electrical work.
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Figure 2 Remove the four screws that hold down the control module box's cover (green arrows), then lift off the cover.
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Figure 3 A brass clip (green arrow) keeps the K40 in place. Pressing it outward sets the K40 free.
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Figure 4 Pull the plugs off the K40 and remove it from the car.
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Figure 5 A skinny flathead screwdriver can be used to pry the relay board out of the case.
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Figure 6 Check the relay side of the board for obvious problems: charred or loose connections, etc.
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Figure 7 Faulty solder connections are most common in the board's upper left corner. Hairline cracks that affect conductivity aren't always obvious. Use the most powerful magnifying glass available to closely scrutinize the solder joints.
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Figure 8 This K40 is fine. The soldering iron dramatizes how full functionality can sometimes be restored by re-soldering joints that have gone bad.
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Figure 9 Electrical contact cleaner can also help the proper voltage get to the various accessories.
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Figure 10 Terminals that affect drivability include the 12-volt main feed (red arrow), fuel pump load (yellow terminal), ground (blue arrow), and fuel pump relay (purple arrow).

Comments and Suggestions

Lida

February 10, 2024

Decent.

Followup from the Pelican Staff:

Thanks for the feedback. Glad it was helpful! - Nick at Pelican Parts

Lucas

February 4, 2024

Hi, i’m having an issue with my 2000 mercedes benz slk 230. I got the car running after installing a new fuel pump but after it idled for about 20 minutes and i shut the car off the car would not start again. After making sure the fuel pump still functioned i checked the voltage going to the pump while trying to start the car and no power was getting to the pump. What could be the issue? The k40 looks fine so im not sure what could be preventing power to the pump. help would be greatly appreciated.

Followup from the Pelican Staff:

Check the feed out of terminal 3 at the relay module. That is power for the fuel pump. If there is no power, check fuse 5 15amp in the module. - Nick at Pelican Parts

Mielaars

December 19, 2023

Hello Team Pelican Parts,

I suddenly have several electrical problems with my Mercedes SLK320 2000/ r170 such as:
- the cental lockingsystem doesn't work anymore the key batteries are okay and de keys have been reset, I can deactivate and activate the car alarm normally and the engine starts and runs normally also
- the windows no longer open or close;
- the direction indicators don't work, just as; the windshields wiper, the rear window heater, the vario roof and finally the interior lighting.

I have no idea what's going on here.
I have checked all fuses and they are all okay.
I also checked the PSE and I can't find any problems with that either.

So can you please help me with an advice?
Thank you in advance for your response,
Peter

Followup from the Pelican Staff:

Might be a fault with the combination control module, as the right rear of the engine compartment. The communication lines to it could be faulty, power / ground issue or the module itself is faulty. - Nick at Pelican Parts

Jason Drake

November 30, 2023

What does the 5 pin input on the far right of the module control. Mine is loose and is causing my car to not start and or die while on the road. 2001 slk 230.

Followup from the Pelican Staff:

See attached. This is all I have for it. - Nick at Pelican Parts

Ambulance 'Driver'

November 7, 2023

I have a 1999 230 SLK auto. I have had a replacement engine due to a blown head gasket and, under load, it coughs and splutters and appears to run on three cylinders and sometimes loses 'Drive'. When you turn it off and start it again, it runs fine until you floor it again. It has new mass flow, new crankshaft sensor, injectors and pump are fine. It runs and starts absolutely fine until you accelerate hard! I wondered if it's the ECU or the K40 relay? I'm stumped! I'm in the UK. Hope you can help and thanks.

Followup from the Pelican Staff:

Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders. Once you isolate what part of the combustion process is causing the misfire, you can identify the root cause. - Nick at Pelican Parts

packerfan

May 21, 2023

1999 Mercedes E300 Turbodiesel Intermittent engine stall:
Engine starts and runs fine but may stall after idling for 10 minutes. Engine will also stall while driving without warning, it happens at low speeds and also at high speeds on Freeway. I replaced the crankshaft sensor and car ran fine for three weeks of daily driving and stalled again. When this happens the engine will crank but not start unless I let it sit for a couple of hours then it will start. Check engine light comes on and fault code is P0200 injector open circuit. when I start the engine I am getting blue smoke from exhaust pipe and it continues to smoke even after reaching operating temperature. What should I be looking for as possible cause for this condition?
Thank you for your help.

Followup from the Pelican Staff:

Sounds like a fueling issue. I would check if the fuel pump is failing or if fuel delivery volume is low. - Nick at Pelican Parts

Carlos

May 18, 2023

The cooling fan in my SLK200 98 starts as soon as I connect the battery. Could this be caused by the k40 module?

Followup from the Pelican Staff:

Could be or a faulty fan. Just confirm the signal to the fan is faulty when the issue is present. - Nick at Pelican Parts

ToKaY

April 29, 2023

Hello Pelican Parts, I have a no crank no start issue with SLK200 r170 1998.
It did always run fine and suddenly last winter all dash lights on but no reaction to ignition switch. The car started by towing and could drive home. Turning engine off and same problem. It didn't start for a few weeks but when I tried to star again fired up without a problem. Then the car was was running fine for 3 months but last two weeks sometimes running rough after startup. Last weeks the same the no start no crank happened again. Tow starting worked again and could drive home.

I found this article and removed the K40. It looks in good condition. Tested all connectors giving signal to the board. Some pins where discoloured. Checked the resistors and three of them read 22 Ohm but two read 66 Ohm. They all have the same color code red-black-black-gold-blue which should be 20 Ohm. Could this be the problem with the start. Or does tow starting and runs fine indicates that the K40 works fine.

Followup from the Pelican Staff:

It is possible, I don't normally use Ohms as a test. I load test circuits, this is the best way to see if they can perform the correct function. Have you confirmed the start signal is missing at the starter yet? - Nick at Pelican Parts

Bryant Barak

February 9, 2023

To the pelicanparts.com administrator, Thanks for the well-structured and well-presented post!

Followup from the Pelican Staff:

Thanks for the feedback. Glad it was helpful! - Nick at Pelican Parts

DucksoupSD

November 19, 2022

I'm a retired electronics engineer and I'd like to suggest that if someone removes their K40 board and discovers a couple of cold solder joints that have opened up, they should just take the time and redo ALL of the joints on the board, not just the ones that they can see are bad now. The boards were made when the electronics industry was transitioning to lead-free solder and the tried-and-true techniques of soldering using lead-based solder didn't work perfectly with the new lead-free solder they've since figured it out. Because the board was not soldered properly originally, every joint will eventually need to be redone. Additionally, unless you've been trained on exactly what to look for, it's easy to miss a cold solder joint that's about to fail. Rather than continue to chase each newly-opened solder joint after being stranded yet again, just take a few more minutes when the board is out and systematically redo completely remove the old solder and re-do with fresh solder every connection. If you, or someone you know or hire, can solder correctly, you won't have any more problems with your K40 board in the long run. I redid all the solder joints in about an hour on my K40 about 8 years ago and haven't had any problems with it since.

Followup from the Pelican Staff:

Thanks for the additional info. We appreciate it. - Nick at Pelican Parts

Sasha

June 10, 2022

Hi I have slk230 1998 . Stops while driving. Need to leave for 30-40 min to start. Fuel pump replaced, battery replaced . Temp is Ok . K40 module looks OK . Gave to electronic shop to be checked. Anything else I need to look into?

Followup from the Pelican Staff:

When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

A-N-T-Z

May 17, 2022

Individual replacement relays are cheap and relatively common, but require the bare relay be removed from its protective cover.
I have a 1999 slk230 which has travelled 117,000km. It began to randomly not start, it would crank i.e. turn-over, but not fire and run. I thought it may have been a bad fuel pump, but i traced it to the fuel pump relay k40k1 which was sometimes okay, sometimes open circuit.
I did think about replacing that relay with the unused adjacent k40k6 air pump relay , but thought I might damage the coil wire if too much heat was applied during the de-soldering/removal process as that very thin copper wire cannot tolerate too much heat for more that a few seconds

The often suggested American Zettler AZ970E open cage relay was hard to find, one on eBay, but the seller wouldn't ship outside the USA, more in Arizona if i wanted to buy 10 for us$120 + shipping
However these are a standard footprint. I looked on RadioSpares and Farnell-element14 websites as they have local offices here in NZ. They didn't have the open cage versions in the required EURO not US - style foot print, but they did have covered sealed versions with that EURO footprint and they were cheap - us$3 - us$6 each depending on the manufacturer

equivalents i found which had the required EURO footprint

Tyco TE Omron P&G OEG Schauk -- V23076 sealed , V23133 open no stock
Multicomp -- CMA4
IMO -- SRKE
Durakool -- DG19

other manufacturers make the same style of relay
for example

Hasco -- CARB
Song Chuan -- 822
Fujitsu Takimisawa -- FRL-274
CIT -- A5
Goodsky -- CAR

most stock was in the EU or the UK with a 5 - 8 working day delivery time to NZ, but one listing in Australia was for V23076A1001C133 at about us$6 and arrived at my doorstep in NZ in under 24hours from order time

It was a SPDT version with sealed glued in place cover. The 2 pieces comprising the cover needed to be removed by cutting so as to accommodate the bus bars which are close to the relay and connect to the cabling terminals. Once those 2 pieces were removed the relay is dimensionally and mechanically the same as the original - 90ohm coil, 1.6W power dissipation, 12-14vDC

So have a look for these cheap common sealed equivalents, and simply remove the casing. It won't matter if you choose the SPST-NO form A or SPDT form C versions, what is important is to choose the EURO footprint version which has different terminal spacing to the US footprint version. Read the data sheets to make sure you have chosen the correct version

some part numbers I thought would work and easily available

SRKE-1AT-SL-12V
SRKE-1CT-SL-12VDC
MCCMA4-S-DC12V-C-E
V23076A1001C133
V23076A1001D133
DG19-7011-35-1012-11

Followup from the Pelican Staff:

Thanks for the additional info. We appreciate it. - Nick at Pelican Parts

Gino

April 20, 2022

I have a 1998 SLK230. Supercharger clutch wont engage and no power to airflap, I checked every fuse and also in the K40 box, all are working??

Followup from the Pelican Staff:

Check if the clutch has power when the ignition is ON. If not, check fuse 2 15amp. In the relay power module. - Nick at Pelican Parts

mike bingham

January 7, 2022

I have 2003 SLK 230 Kompressor with 65,000 miles. I just purchased a K 40 module from uou. Thanks. I get it in a day or two. The three solder connections everyone mentions on the pc board are fine but i found 6 solder points that are dark grey to black. I bought new board based on this.

Question - I was able to trigger 3 of the 5 relays in the old module. Is this normal or should all 5 trigger with the 9 volt battery?

Followup from the Pelican Staff:

Going by memory, three are triggered together, the other two are controlled separately, on individual circuits. - Nick at Pelican Parts

mel

May 31, 2021

hello

want to let you know that i found the culprit of my hazard and indicators issue on my 2001 slk 320 ,i removed the confort module also called n10/3 and it was colpletly burned arounf pin 45-46
i ordered an other one but before replace it i would like to know if a short circuit has caused and what is the cause or is it due to normal wear after 20 years
do you know which part or function is controled from pin 46 in order to check if all is ok before installing new module

Followup from the Pelican Staff:

For the short, check the load the relay supplied voltage for. It is more than half the fuse rating for the circuit? Use an amp probe to test. - Nick at Pelican Parts

mehl

May 23, 2021

thank you
last question , could you tell me if there is a warning beeping on slk320 when passenger door is open ?
i know there is one when driver door is open when you forgot to turn off light but due the continus beeping i can’t know about passenger side door switch if working properly

thks

Followup from the Pelican Staff:

I replied to your latest comment. - Nick at Pelican Parts

mel

May 18, 2021

already checked with tool and no code fault recorded at all
i also checked doors switch and seems ok but check again
problem is even if i resolve beeping sound i am in loss

with indicator / hazard not working at all
what do you mean by « modul is faulty « wich modul?
and replace chime ? what is chime ?

thks

Followup from the Pelican Staff:

The module that makes the chime sound may be faulty. YOu will have to test the inputs and switches that trigger it to confirm . With your vehicle info handy, give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need. - Nick at Pelican Parts

mel

May 18, 2021

yes the beeping sound is when i turn ignition and still remains in driving condition making me crazy !!
it is the same alert sound when you forgot to turn off lights module and open the door
apparently there a little part in the ignition lock called
« light warning buzzer but dont know if the sound come from this buzzer what is the exact function of the buzzer ? or if there is an other buzzer in the instrument cluster ??
if ignition is the issue is there any relation with hazard / indicator fault ?

Followup from the Pelican Staff:

Yes, so either the module is faulty or a door is being seen as open. Use a scan tool to check door switched and any other item that would trigger the warning. If none are triggering it, replace the chime. - Nick at Pelican Parts

mel from france

May 12, 2021

hello

i have slk 320 so no k40 relay for this engine but i have a crazy beeping sound from dash and no warning light and hazard
i tried to change turn signal/hazard relay located in the trunk but does not work
it sound like a seat belt not locking but i tried many many option and still same issue
i dont know if the beeping is due to the hazard and turn signal issues but impossible to find out what is the problem
i scanned the car and no fault codes at all
friend told me probably the instrueent cluster fail but not sure
also i tried to replace hazard switch ans still same
have you any idea of the problem ? is there any place on the slk 320 where there is an equivalent of k40 relay ?

thanks

Followup from the Pelican Staff:

Does it sound like the key in warning? If so, the contacts in the ignition switch could be faulty. - Nick at Pelican Parts

peter

May 4, 2021

thank tou for your help it was the fuel pump relay

Followup from the Pelican Staff:

Thanks for the follow up. We appreciate it. - Nick at Pelican Parts

pete

May 2, 2021

i have mercedes slk 230 1998 wont start no fuel pressure car run when 12v to pump k40 fuel relay car starts ok if i hold contacts together when let go engine stop do you think a need a new relay pack

Followup from the Pelican Staff:

I would test the relay. is it being commanded ON? if so and it will not hold ON, the relay is faulty. - Nick at Pelican Parts

momo

May 1, 2021

Hi again from momo, i still have same problem in my k40 . car not starting and fan running fast. if you looking to my story message ,i changed no3 in my k40 . But before start i have to put toothpick behind fuse no3 beside flew fuse to stick together platinum. then i stick platinum together with toothpick very quickly, i telling my wife starting and i put k40 inside the box and close the lid and driving with car but when i want to switch off each time every single day,must take out toothpick ,then switch off. and thats a very hard job everyday. but now my car got new problem, it looks like work with 3 cylinder . the engine has very low power, shaking engine so much and empty my petrol very quickly. ive been many years engineer for the tanks in the army. i changed all spark plug and the wires is fine. when i check the car coil, all for cylinder is fine but the engine still shaking. it must be some where else, oxygen or petrol pressure or many others parts fault. these 2 parts that i sent photo, i dont know what the names are. one of them looks like electronic pump . for 2 months when car running , it was very noisy same automatic gun toys but now , no voice and photo no2 black picture i clean it with spray but when i disconnecting this its nothing happened.
question no1 : what is the problem to k40?question 2 : what the name of these two parts are?
question no3 : where in the car can be wrong engine shaking and not power when all four spark plug are fine?
qustion no4: could be these 2 parts not working , thats why engine shaking and not power?
anyway i had only one child 25 years old. he died lst yer in car crush in sweden and this was his car and the last memory for me. many garage charged me but they couldnt find the problem. can somebody please help me? thank you very much, Momo

Followup from the Pelican Staff:

1. I do not know exact issue with the K40. You will want to get a wiring diagram and trace the voltage loss to the source. Could be as simple as a fuse. i do not have wiring to consult. 2. I replied to your other posts. 3. Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders. - Nick at Pelican Parts

momo

May 1, 2021

1998 slk 230 photo av the part 2 name?thank you

Followup from the Pelican Staff:

That looks like an oxygen sensor connector. - Nick at Pelican Parts

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momo

May 1, 2021

Hi sorry 1998 slk 230

Followup from the Pelican Staff:

Got it, thanks. - Nick at Pelican Parts

momo

May 1, 2021

Hi what is name this parts 199 slk 230

Followup from the Pelican Staff:

Need you to take the photo from farther away so I can identify engine also. - Nick at Pelican Parts

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momo

April 24, 2021

Hi and thanks. i still have engine checking and k40 saime problam sa i said in my last massegs i need name this 2 part on 1998 slk 230 mybay the not working.thank you

Followup from the Pelican Staff:

Can you share a phot of the part you are looking for the name of? - Nick at Pelican Parts

peter

April 24, 2021

i have a slk 230 1998 wont start starts up with brake spray into air take check fuel pump no live connect live 12v to pump car starts checked k40 relays no bunt solderlooks all ok help please

Followup from the Pelican Staff:

Check the fuel pump relay. It is located in the right rear of the engine compartment. Check if it is being activated, if it is and lacks power, check fuse 3 and 5. - Nick at Pelican Parts

Rommel

April 17, 2021

Hi Nick,

quick question, is there a starter relay for a 1997 SLK230? if they have, do you know where i can find them? many thanks.

Followup from the Pelican Staff:

I believe it has one, I however do not repair info with the location. With your vehicle info handy, give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need. - Nick at Pelican Parts

Cole

April 6, 2021

Thanks Nick for your response. I did further testing. There is no fuel at the fuel rail valve. I check the relay board and looks fine. There is power at the fuel pump but not running. The vehicle will start with a quick test with starter fluid.

Followup from the Pelican Staff:

Sounds like the pump is faulty. Just confirm the power and ground feed to the pump passes a voltage drop test, if so, replace the pump. - Nick at Pelican Parts

cdt1983

April 3, 2021

Have a 1999 SLK230 ‐ turns over but will not start, inspected k40 and looks good...I don't necessarily hear the fuel pump with ignition on but there is a noise similar to it under the hood when I turn ignition on. Is there Schrader-like valve I could check for fuel at the fuel rail? I don't smell any fuel...not sure I would though. thanks for any insight

Followup from the Pelican Staff:

I can't offer any helpful insight without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

momo

April 1, 2021

Hi and thak you .i going to open ignition swigch and let you know.many thanks

Followup from the Pelican Staff:

Let me know how it goes. - Nick at Pelican Parts

momo

March 26, 2021

1998 slk 230
fuse number 3 on the k40 board for power engine

Followup from the Pelican Staff:

Fuse 3 should get power when the key is in the run or start position. It could be a wiring issue or fault in the ignition switch. You can test power to fuse 3 at the back, then trace the wire using a wiring diagram to the source. Or simply add fused power to see if the problem is remedied. - Nick at Pelican Parts

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momo

March 26, 2021

K40
1998 slk 230
R170

Followup from the Pelican Staff:

I replied to your other comment. - Nick at Pelican Parts

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momo

March 26, 2021

Hi every one,my last question was on oct 2020 and you can see the story of my car problem. i still have the same problem and i hope somebody help me. ive been in many years for the tanks engine for the army. i checked any parts i knew. last answer from Mr Nick thanks for reply back. i explain again the problem shortly. My car is 1998 SLK compressor 230 R170 not starting sometimes and fan running fast speed. i brought home K40 as you told me and checked 5 fuse on the k40 board. the number 2 is for flue was fine. But 1 of them number 3 for power engine not working and because k40 is £200 ,i bought from ebay just 1 fuse. with soldering i chenged number 3 fuse very nicely. i put that back in the car but not in the box and asked my wife to start the car so i could see all 5 fuses platium when the power coming to k40 ,4 fuses platium working when i tried with screw driver to stick together platium each fuse. so i saw just fuse number 3 as i changed still not working and i found the problem why car not starting and fan running fast but general problem i cant find yet because when my wife turn the switch on before starting,i put some toothpick behind platium fuse number 3 and do stick negative to oposite and car started very well . i can go to job and come back but with big stress because if the toothpick fell down and platium fuse number 3 be opened and leave each other, car be off in the middle of the road. can you believe how difficult it is? each time must somebody start for me and i running out open the big black box lid beside the battery .second i took out k40 box and put toothpick behind platium so i hope somebody can help me why fuse number 3 platium not automaticly be same magnet together. do you think i have to change flue fuse number 2 as well or is there any other fuse some where not sending power to fuse number 3 for start? also this was all job i done myself as engine engineer but also i brought the car to garage for 17 days i waste the time and they charged me £100 and they cheat on me and said we change the full board k40 but i knew my soldering so please somebody help me why power not coming to fuse number 3 for engine start. i try under the name of Momo to send a picture of the fuse and k40 for more understanding what i mean. i dont know how i can send photo to this site but you can see the photo of the fuse number 2 for flue as Mr Nick sent me on october 2020 because all car is similar. thank you very much and im looking forwards for any help

Followup from the Pelican Staff:

Fuse 3 should get power when the key is in the run or start position. It could be a wiring issue or fault in the ignition switch. You can test power to fuse 3 at the back, then trace the wire using a wiring diagram to the source. Or simply add fused power to see if the problem is remedied. - Nick at Pelican Parts

American Mini

December 13, 2020

After removing k40 module on my 97 E320 I noticed the "blower fan" was not working. How do you replace it and how do I find one?

Followup from the Pelican Staff:

Are you looking to replace the blower or the relay? - Nick at Pelican Parts

momo

October 28, 2020

hi and thanks
1998 slk 230 komprssor
not spark not comperssion
just not starting and fan run fast speed and not any mor fule voice.and sam times start and everything com to normal but when i swish off agen not strting and fan runing every 50 times start one time car starting and now im very sad for this car .thanks

Followup from the Pelican Staff:

Could be an issue with the fuel pump. I would perform a fuel delivery system test. Check fuel pressure, volume and quality. - Nick at Pelican Parts

Momo

October 23, 2020

hi and thanks
i have chenge fuse 40 not staring
are you think i must buy new box k40?

Followup from the Pelican Staff:

What is the year and model of vehicle? What is preventing the vehicle from starting? Spark, fuel or compression? - Nick at Pelican Parts

bess koliqi ireland

October 22, 2020

hi all .the SLK 2001 F40 multi relay box gives trouble the relays are batch of cheap relays mercedes fitted. the fuel pumps cuts out wont work,wont start. its the second relay for the pump ,after the horn one.to sort out the fuel pump relay do piggy back with soldel iron 4 wires at back of faulty relay and bring them out the box and connect to new relay on those wires,done, decommission the old faulty the fuel pump relay then, its aall be fine

Followup from the Pelican Staff:

Thanks for the Info. We appreciate it. - Nick at Pelican Parts

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momo

October 20, 2020

Hi
my 1998 slk 230
not starting and fan run fast speed
i had cheked k40 and all fuses and coolant sensor and any wire i checked and claeaned with electrical spray
i took out competely k40 box ,it was fine . and changed coolant sensor.
changed my key battery fob . and charge the car battery . also i have no any elecrical ohm meter tools.but still not starting . but sometimes car starts and everything working fine but when i switch off, again not starting or in the middle of the road and behind treffic light again car be off and not starting. just fan runs fast speed and you can't hear as usual flow pump voice. i had checked break pedal as well. i had no any electrical tools but i was good army tank engineer mechanic but of course car and army tank are diferent.
can somone please helping me to take out
This ghost from my car ??😜

Followup from the Pelican Staff:

Could be an issue with the fuel pump. I would perform a fuel delivery system test. Check fuel pressure, volume and quality. - Nick at Pelican Parts

Tom

September 10, 2020

Hello, I have a 98 slk 230, will crank but not start after being left in the garage for some time. Have checked and resoluteres k40, quick question; what is the yellow and purple supply situation supposed to be? Yellow primes for a couple of seconds and deactivates, purple blue wire loses power after cranking.

Followup from the Pelican Staff:

The yellow on your vehicle is for the horn relay. from the wiring I found. Do you have wiring to confirm it is a power supply? Purple should be power when the key is ON. - Nick at Pelican Parts

Stephan

June 14, 2020

I have 2001 slk 320 no crank, fast cooling fan. New battery, horn and air pump work. 12 volts to image 10 with red arrow. I soldered the the three suspect pins and even swapped out the the entire k40 relay block with a used one. Ordered a coolent sensor and will swap it out once i get it. What else can I try?

Followup from the Pelican Staff:

Have you confirmed your solders repaired a lack of power from the relay? - Nick at Pelican Parts

MGBmbzguy

March 9, 2020

1998 SLK230 runs fine but no supercharger. Only recently displayed P0341 & P0410 codes. New plugs, coils, wires, MAF, crank sensor, cam sensor, filters etc. as it was at 280K miles and started missing at higher rpm and went into limp mode. After all that it turned out to be the K40 as I switched it with a spare I had and all was excellent until the "no boost" a week ago. Already confirmed the clutch works on the S/C. and I did not mess up any wires / hoses during the previous work. Car has the performance of our '68 MGB now...... Help?

Followup from the Pelican Staff:

Check bypass valve function. See attached. - Nick at Pelican Parts

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DaveS

January 31, 2020

Just want to say a big THANK YOU for the "how-to" articles. They have been very helpful over the past few months. I used to split my car repair and maintenance part purchases over three different companies but now I give all my business to Pelican parts.

Followup from the Pelican Staff:

Thanks for the feedback. Glad we could help. - Nick at Pelican Parts

keith

January 19, 2020

Thank you for the reply.My car is a 1997/1998 R170 slk 230,so an early one nick.

Followup from the Pelican Staff:

Check the relay for power. You can simply jump it out and see if the pump runs. Check fuse 5 and 3 in the front relay module, they are for the relay. - Nick at Pelican Parts

keith

January 15, 2020

Hi Nick.
i have no voltage at the load wire for the fuel pump.I have run the K40 on a friends slk without issue so not the k40.Pump removed tested runs all ok.All fuses ok, no fuel pump running at all. Any ideas please.

Followup from the Pelican Staff:

What is the year and model of vehicle? I can check if I have wiring for it to review. - Nick at Pelican Parts

Mark

September 25, 2019

hello,
mercedes w215 cl 600 v12 2001, turn on key suction fan goes on but not in a mode that is not normal very high speed dash board lights up everything works except th engine wont turn over. And randomly it might start for a minute. suction fan comes on and engine shuts down. NO DTC CODES. I took out the fuse for the suction fan and it showed up as no V to fan !!! I am stupefied.

I have 25k miles never been in the rain of snow looked at every connection, and grounds sprayed connections with electronic connect spray Any Ideas ????

Followup from the Pelican Staff:

I can't offer any helpful insight without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are any components missing power? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

Roland

September 10, 2019

Hello, I own a 2002 E320 sedan, for the last 2 years I have been driving with the problem of whenever the BAS ESP code come on, the air conditioner blower motor will stop blowing, both turn signals can't operate. These problems normally won't happen in the early morning when temp outside is cool and definitely happen when temp is hot, is this related to the K40 or the lateral accelelation module or something else? About a year ago, I found out a temporary solution is if I need to make a turn, I jiggle the ignition switch then it turns on turn signal and blower together momentary sometimes for a short time. I Applicate very much for your information.

Followup from the Pelican Staff:

Focus on one issue. For example,the turn signals. When they are not working, is the switch missing the ignition power feed? - Nick at Pelican Parts

Nick

August 4, 2019

I have a 1999 slk 230 speedometer stopped working top no longer goes down and wont shift out of 1st gear, codes P1605, P0500-25, P0600, P1747, I have replaced right and left rear speed sensor. Any ideas?

Followup from the Pelican Staff:

Do you have the fault code descriptions? - Nick at Pelican Parts

Robert

August 1, 2019

Please help. SLK 320 2001.The mech pulled the cap off the k40 relay and six wires came loose and he does not know which color wire goes where. Please if you can send a photo or instructions of what color wire goes to where.

Followup from the Pelican Staff:

I don't have wiring for your vehicle to share. I would suggest you grab a repair manual, you should own one. It will have it. Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts

Pete

July 31, 2019

I have a 2004 230 3.2L. I am getting a check engine light randomly. I have a P0410 code, Secondary Air Injection System Malfunction.

The troubleshooting info says to replace K40 Relay Module w/P2023. What is the P2023 part of this module?

Followup from the Pelican Staff:

I believe that is an intake runner control valve. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need. - Nick at Pelican Parts

Maximan

March 26, 2019

Interesting though ,your answers are,they seem to say "lots of the time " you don't have a wiring diagram I can't understand why this is if you are a problem page.
Horn not working on my SLK 230 2003

Followup from the Pelican Staff:

it is a technical article about a known issue, not a technical support hotline. We do try to answer questions as we can, but we don;t have repair information for every vehicle manufacturer, so our help is limited to what we have or know. - Nick at Pelican Parts

Peter

February 20, 2019

I opened the K40 like you have shown in the photo. Took it to an electronic repairman. He hook up a 9V and 1.5V battery and tested the relays. The fuel pump replay has no response. He took the relay out and found the hairline copper wire in the coil is broken. He replaced the relay with a spare one he has old part from split type air conditioner circuit and hold it in place with some thick silicone glue. The whole troubleshooting + replace relay need less than one hour. I put the K40 back into the car and fuel pump working and start up no problem.
He also found some minor cracks on the wields. Lead-free stuff won't last, he said. Fix them as well.
The K40 replacement cost at least $2000 here. The electronic repairman charge me $400.

Thanks for the advice Pelican Parts.

Followup from the Pelican Staff:

Thanks for sharing your repair process and experience. These type of comments add so much to the Pelican tech community. - Nick at Pelican Parts

John0132

February 11, 2019

Referencing my earlier question, Internet research indicates the fuel pump relay is part of the K40 relay, and is referred to as the k1 relay.

My question therefore changes to this; can you explain the difference between the purple arrow fuel pump relay and the yellow arrow fuel pump load on your K40 illustration?

Based on the relative wire sizes, it would appear that the fuel pump load plug actually connects to the fuel pump. Not sure what the fuel pump relay wire does?

Followup from the Pelican Staff:

Replied to your earlier question. - Nick at Pelican Parts

John0132

February 9, 2019

My 2002 SLK recently died on me. Turns over but no start. I determined I have no fuel pressure. I also noted that I no longer hear the electric motor sound when I turn the ignition. I assumed this was the fuel pump.

My question is this: To begin troubleshooting, is the fuel pump relay part of the K40 unit? Based on your explanation of the K40 terminals above, I would assume it is.

Followup from the Pelican Staff:

The relay is part of K40. See attached wiring. The pump is grounded at K40 also. - Nick at Pelican Parts

Peter

January 30, 2019

Hi, 2003 SLK R170. Fuel line detached to check fuel supply. No fuel. Fuel pump detached. It is working after feeding electricity to the detached fuel pump. It runs.
Fault codes:
K401k1
N27
N10/2kA

Any advice on what should be replaced?

Many thanks.

Followup from the Pelican Staff:

Replied to your earlier comment. - Nick at Pelican Parts

Peter

January 29, 2019

2003 R170. Opened fuel line, crank engine, no fuel passing. Fuel pump removed and tested working by feeding electricity to it. Error codes:
P2017 004
K40k1
K27
N10/2kA
Any advice? Many many thanks.

Followup from the Pelican Staff:

I would need the fault code descriptions to see if I have info for them. - Nick at Pelican Parts

Victoria MAC

December 2, 2018

Received the part from Pelican and had it in and up and running in 20 minutes. All the error codes have disappeared and no more issue with stalling. Great instructions!

Followup from the Pelican Staff:

Thanks for the feedback. Glad we could help. - Nick at Pelican Parts

hollandbuick

November 21, 2018

would a fan under the module control box on my slk230 cause the modules to burn out and cause a no start error?

Followup from the Pelican Staff:

If a wire shorted and blew a fuse, yes. - Nick at Pelican Parts

aardvark66

October 26, 2018

1997 SLK230. Starts fine but smells like it is running very rich upon startmy anosmic friend can smell it. If i take off slowly it is stumbly and awful if taking off up a slope, if I accelerate hard then it just dies for a second or two and then takes offat any speed. If I rev it hard while stationary it sometimes will stall when the revs drop. Compression is OK. Changed plugs today but still no change to car's behaviour. It has been suggested that I change the coil packs as my next step. I have cleaned the MAFS. Currently have a leg injury which stops me from being able to get to the o2 sensor so I hope it's not that. Any suggestions? Please?

Followup from the Pelican Staff:

Check resting fuel pressure, does it hold? What is spark KV max? - Nick at Pelican Parts

Andy

October 18, 2018

Hi Nick

My wife's 1999 SLK230 engine has cut out 3 times over the last 4-5 months. The first time she said the cooling fan was running flat out and the engine refused to crank. It started and ran fine after an hour. The 2nd and 3rd times it just cut out however she was able to immediately re-start. No fault codes and it runs like a dream otherwise. Could this be the infamous K40 problem? Many thanks Andy

Followup from the Pelican Staff:

Could be. I can't offer any helpful insight without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

faze

September 23, 2018

Hi Nick, I have a '99 SLK R170 auto. engine has cut out whilst travelling at around 60mph at night with headlights on. The only problem on both occasions was one reverse light out, I have replaced bulb without problem, could the reverse light out cause engine cut out. BAS SAR light comes on when engine cuts out. when restarts all dash warning lights go off as normal. thanks in advance for your help

Followup from the Pelican Staff:

I don;t think that bulb would cause that. You'll want to see what is missing when the engine stalls and won't start. Fault codes, etc. - Nick at Pelican Parts

SLKJim

August 26, 2018

Where can I get a wiring schematic for a 2001 SLK320. I can manual close the contact on the relay for the fuel pump and get the car to run but not sure where the relay gets it signal to run upon having the ignition swith to the on position and i understand the pump should only run for 20 seconds once placed in the on position and upon starting.

Followup from the Pelican Staff:

Alldata or a Mercedes repair manual. - Nick at Pelican Parts

zookeep

August 9, 2018

ok 2 codes found p0500 and p1747, the front left tire was off for a bit and got wet could the speed secor going bad cause the hole prob?

Followup from the Pelican Staff:

The p1747 is likely a faulty gear selector. The p0500 is for a fault speed sensor signal to the trans controller. - Nick at Pelican Parts

zookeep

August 9, 2018

1998 slk230 sat for a few weeks for new tires when I ran it was now stuck in 1st and speedometer does not work, abs,brake, and asr lights on dash stay on.

any1 have any ideas? tranny was rebuilt 2 years ago and not put a hole lot of miles on it yet

Followup from the Pelican Staff:

I would start by checking the vehicle for fault codes. If the system is not working properly, a fault code will be set. This will be your best bet when diagnosing. - Nick at Pelican Parts

Matthew

July 23, 2018

Can the K40 relay cause issues with the supercharger? Also, can it affect the PSE pump for the central locking system?

Followup from the Pelican Staff:

I would need to see the wiring diagram for your vehicle to comment. Wiring diagrams vary depending on model and year. - Nick at Pelican Parts

DaveO

June 1, 2018

Not yet got the diagnostics read. A friend has a saloon with the same engine, I'll bribe him to test his k40 in my car as no breakers have the part.

Followup from the Pelican Staff:

let me know what you find. - Nick at Pelican Parts

DaveO

May 21, 2018

Hi

SLK 320 2003

The ESP and ABS lights wont go out, checked battery & alternator and they're fine.
After a week the engine warning light came on. Disconnecting & replacing the K40 turns the Engine Warning light of for a while.
Had a close look at the K40, everything looks fine except for a little residue on the contacts on the biggest relay which I cleaned.
Trying to find a K40 from a breakers yard to either fix the problem or confirm it's something else.
I'm open to any other suggestions.

Followup from the Pelican Staff:

What fault codes are stored? - Nick at Pelican Parts

greg

May 3, 2018

1999 slk230 ,it was running and starting fine but the battery was stone dead ,i replaced the ,battery,keys,starter,fuel pump,,the motor would turn over as long as you held the key ,but now it only turns 2 revolutions spits and stops turning ,wth the old battery and a jump it ran fine. im out of money to throw at it so i need all the advice i can get,i did notice the tach is stuck on 2000 and the temp on 80 when i turn the key they dont move

Followup from the Pelican Staff:

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

greg

April 22, 2018

my slk230 will spin over 2 times try to crank but wont ,i replaced the battery ,starter ,fuel pump ,and looked at the k40 ,it was running fine b4 i replaced the dead battery,but now 2 turns and it just quits

Followup from the Pelican Staff:

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

osvaldo

February 15, 2018

Do you know where the wire that is connected at the terminal showed with the arrow purple come from? in order to identify why dont have electricity power thanks a lot

Followup from the Pelican Staff:

I believe it goes through the panel to the fuel pump relay. I don't have a wiring diagram to confirm that for sure though. - Nick at Pelican Parts

osvaldo

February 15, 2018

thanks for your answer. But do you know why dont have electricity power in this wire identified with the arrow purple in the picture 10?

Followup from the Pelican Staff:

I believe it goes through the panel to the fuel pump relay. I don't have a wiring diagram to confirm that for sure though. - Nick at Pelican Parts

osvaldo

February 14, 2018

hello I have a mercedes w210 e320 1996 does not turn on no power to the purple conector figure 10 arrow purple that give power to the coil that command the gasoline pump in the relay k40. what can happen that there is no electric power in the conector see your picture10 purple arrow?

Followup from the Pelican Staff:

No power there, fuel pump will not run. - Nick at Pelican Parts

osvaldo

February 14, 2018

I have a mercedes w210 e320 1996 sometimes starts and sometimes no.I have detected that I do not get current to the wire showed in your picture in colour purple that give power to the coil of the fuel pump into the relay k40

Followup from the Pelican Staff:

No power there, fuel pump will not run - Nick at Pelican Parts

Ben

February 10, 2018

I have had a 2001 M/B 230 Kompressor. There are times when the radio functions just so-so; the electric seats do not work at that time; and the tail light assembly isn't as bright at the other. Then, at other times, all three work great. What do you suggest? Thanks!

Followup from the Pelican Staff:

First, I would test the starting and charging system. - Nick at Pelican Parts

ary

January 30, 2018

Hi, my first time here. My MB 98 SLK230 work fine until 80 grado, after thet, if you turn off and tern on it start, after 15 min don't start until engine cool, I was thinking bad Crankshatf, but I disconect it and work likewise. How can work without Cranshaft? Sometime I got Cod 0340. I saw that de ECU fan dont work due no electricity and not fuse in between. I appreciate any help.
Congratulation for this site. Thank you

Followup from the Pelican Staff:

It can start using the camshaft sensors if the crank sensor fails. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.- Nick at Pelican Parts

Haasholio

January 7, 2018

96 E300 D cranks but no start after running out of fuel. Replaced filter and verified fuel all the way to injection pump, but no fuel at injectors. How do I check voltage to the shut off valve, and what energizes the SOV. K40 problem?

Followup from the Pelican Staff:

Does the fuel pump have power and ground? Possible the pump burned out from being run low on fuel. - Nick at Pelican Parts

stevem

December 24, 2017

Been having intermittant starting problem with 2004 slk230.
Pulled the k40 box and found dirty contacts. Cleaned and so far so good. thanks for the tip.

Followup from the Pelican Staff:

Thanks for the feedback. Glad we could help. - Nick at Pelican Parts

Randy

September 4, 2017

fyi, the red and green lights flash when key is on and cranking. We have re-synced the keys many times and recently purchased new keys.

Followup from the Pelican Staff:

I responded to your earlier post. - Nick at Pelican Parts

Randy

September 4, 2017

Have a '96 c-36 AMG, problems are crank but no start. Have had many shops try to repair, and spent lots over several years, only to have problem re-occur. Last shop offered to try to bypass immobilizer. In reading posts, should I try the k40 relay? Where do i locate on the c-36. Wife loves her car, but afraid to be stranded again.

Followup from the Pelican Staff:

You can't bypass the immobilizer, it will fail again or set different faults. Engine start will be blocked. What fault codes are stored? - Nick at Pelican Parts

Mike

July 9, 2017

1998 SLK230 is the car in question.

Followup from the Pelican Staff:

Got it, thanks. - Nick at Pelican Parts

Mike

July 9, 2017

I should have given some background to my comments. CAR cranks, NO start.

Followup from the Pelican Staff:

Got it, thanks. - Nick at Pelican Parts

mike

July 9, 2017

First -thanks very much for this website. Here the problem I'm having just today. I have a fully charged battery and engine cranks strong. I've replaced the fuel filter and checked the k40 card for obvious problems. It looks good. During eh start cycle I see no fuel coming from the schrader valve but here the fuel pump running. I also here the "distribution Pump" under the hood running as well.
My thought is this pump has gone south, and needs replacement.

PS- I can't feel any blower air in my electronic module box. Where is that blower motor you spoke of. Thank you kindly for your help.

Followup from the Pelican Staff:

Could be an issue with the fuel pump. I would perform a fuel delivery system test. Check fuel pressure, volume and quality. You'll need to test these items to be sure. - Nick at Pelican Parts

boy roy

July 1, 2017

your problem is a loose connection on the single wired plug on the left hand side of the k40 relay if it has been a bad connection for a while the you may have to check the pin if it is burnt then clean it






Followup from the Pelican Staff:

Thanks for the additional info. We appreciate it. - Nick at Pelican Parts

roy.halaby

May 25, 2017

Hello, i have a slk230 1997, i have a problem, from time to time , my supercharger stop working for a couple of minutes , and then it starts working on itself, my mechanic told me that we have to try changing the bypass valve to see if that's the problem, any suggestions?

Followup from the Pelican Staff:

It could be the bypass valve, that would prevent boost from occurring if it were malfunctioning. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.- Nick at Pelican Parts

Allen

May 10, 2017

On '01 SLK320, I show the same configuration of K40, as pictured above. At top where F4/40amp fuse is located the five fuses to its right are labeled, in order, F3,F5,F1,F2,F6. I never get power to F3 or F2, ign. switch on or off, either side of fuse. That mean that K40 is defective? Should I do a soldering check?

Followup from the Pelican Staff:

Check solders to see if there are failure points. - Nick at Pelican Parts

auctionsco

May 10, 2017

just bought a 1998 mercedes clk 320. 10 milesw later it suddenly dies on freeway and wouldn't start or turn over. all electrical incl. windows, roof, lights are fine.
I towed to MB mechanic. After 3 hrs. he thought F40 relay.
That didn't fix now he wants to install $1400 ECM. I'm hauling it the 150 miles home today. where to start?

Followup from the Pelican Staff:

When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

Dragon06

May 9, 2017

Today I went to take my 1998 SLK 230 out of winter 4 month storage as I have for over a decade. Since all of the annual services, etc are performed each fall, I pull the cover, do a fluid check, verify that no critters are in residence, and re-install the battery.

This time, as soon as the battery negative terminal was connected, and with no key in the ignition, all of the instrument cluster warning lights illuminated, the fan engaged, and the exterior parking lights illuminated.

I disconnected the battery immediately, and am now trying to trouble shoot the problem. Any assistance is very much appreciated.

Followup from the Pelican Staff:

hard to say. Sounds like a short to power. I would check if the ignition switch is sending power to the fuse panel when it should not. - Nick at Pelican Parts

Gouchybear

May 2, 2017

Hi All I have a 2001 SLK320 Sport and was having the same symptoms as others on here. When I was removing the K40 relay from the module box under the hood I didn't notice the harness clip for the F4 set of wires had sprung open and all the wires came out of the harness. Can anyone help me with a picture of the correct wire sequence so I can reassemble the harness? I would appreciate it very much!

Followup from the Pelican Staff:

I don't have wiring info for your vehicle. I would suggest you grab a repair manual, you should own one. It will have the wiring and connector info. - Nick at Pelican Parts

Deborah

April 26, 2017

All fuses have been replaced . Like I said 2 months ago I drove it about 12 miles to a local store came out it wouldn’t start .... no sound at the ignition but lights uses and parts you mentioned have been check.... all fuses have been replace except for the ones under the hood in the black box , radio worked, fan revived up. It set for day. I got new battery, new fuses, changes batteries in remotes etc. Dove it several times everything seemed fine.... except occasionally the power seats would not work but after I drove it for a few minutes I could adjust my seat. This past Friday I started it ...it cut off. Started it again ...it seemed fine with the exception of the power seats. ON my way about 200 yards it cut off in the middle of the road. I have electric... Dash lit up but no codes as you mentioned. Fan ran high and fast. My brother popped the hood took out the 40 amp wiped it off ...insert it back in and it started right up. I haven’t drove it since ...I'm afraid it will shut off on me in traffic and cause and accident .

Followup from the Pelican Staff:

Do not drive the vehicle. Test the items I mentioned in my previous reply. You have to determine why it is not starting or stalling. - Nick at Pelican Parts

Deborah

April 25, 2017

Hello,
I have a Mercedes slk320 2002. I either not starting or shutting off while I'm driving it. just started having problem's with it. When I turn the key all dash light come on and fan sounds like a jet taking off. All ELECTRONICS componate work but the car wont start. I have a brand new battery ..... my brother checked everything ..... I couldn't even jump the car to start it. The final thing we did was pull the 40 amp out wipe it off and it started. Is the 40 amp working loose or should we look for something in the wiring in the black box ??? ALSO SOMETIMES MY POWERS SEATS WORK AND SOMETIMES THEY DONT


Thanks
DEB

Followup from the Pelican Staff:

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

Ryan

April 23, 2017

Hello. I have a 1998 slk230. The right blinker dose not come on. The left works fine and the hazzards work fine as well. Just no right turn. When I turn the blinker on it clicks just does not light up. Do you think this is a k40 issue? No blown fuses

Followup from the Pelican Staff:

Not likely. Have to confirmed the stalk is getting power and sending the same signal to the right as it does the left? I would start there. - Nick at Pelican Parts

Stealth

March 28, 2017

Hi Nick, to jump the K40 relay to confirm it cranks do you connect the 12-volt main feed on the relay red arrow in figure 10 to the car battery? What connecter is best to use?

Followup from the Pelican Staff:

I usually make a fused jumper wire. - Casey at Pelican Parts

leon

March 27, 2017

My 2000 mercedes 230 slk's radio stays on when key is turned off?

Followup from the Pelican Staff:

Sounds like a faulty radio. - Casey at Pelican Parts

Stealth

March 18, 2017

Hi Nick, I have a UK RHD R170 SLK 230 with all the symptoms of a K40 relay fault engine cut out, LIM light on, fast engine fan but no engine crank. A garage has told me there is no signal from ECU to diagnostic so they think it needs a new ECU. Could the ECU cause these same symptoms? How do you jump the K40 relay to confirm it cranks?

Followup from the Pelican Staff:

Wiring for each K40 varies. SO, easiest way is to grab a wiring diagram, find the constant power to the relay, then jump that to power all the fuses int he relay. Does the vehicle start and communicate?- Nick at Pelican Parts

Patri

March 8, 2017

i have a 2002 320SLK random no crank starter not working worse when car warmed up. Turn key all lights come on i can hear fuel pump. the time that it wont crank the P in the drive indicator is just a black box. try key several times and eventually car will start. Also when the P is not present if a shake the K40 relay i can get the P to appear and the car will start. Just asking before i buy the relay..

Followup from the Pelican Staff:

if agitating the relay makes the vehicle start, I think it is safe ti replace it. You can try removing and jumping the relay to confirm it always cranks with the circuit bypassed. - Nick at Pelican Parts

Cookie

January 20, 2017

Hi nick, great guide to the K40 & thanks for continuing to post useful guides on other topics! I've got a code on my Slk 2002 230 R170 = c1010 which is undervoltage at terminal 87 - is this related to the k40? Also my rear screen demister isn't working at all - is this also related to the k40 unit? If so what terminals can I check on top for these 2 things? Many thanks

Followup from the Pelican Staff:

it could be, as 87 is switched power. bext bet, backprobe the K40 output, check for battery volts. if battery volts are present, load the circuit and confirm viltage it steady. if it drops, replace replay. - Nick at Pelican Parts

Tina

January 12, 2017

We were jumping from the 12 volt feed indicated by the red arrow to the fuel pump load indicated by the yellow arrow to get power to the pump and car starts. We also discovered we don't have power to the fuel pump relay with the key on. Is it still likely the problem is in the K40?
99 SLK

Followup from the Pelican Staff:

If the panel is getting power, but not at the relay, the panel may be faulty. best bet is to get a wiring diagram and cofirm the power is present. - Nick at Pelican Parts

Tina

January 11, 2017

the fuel pump load section of the K40 is getting no power, we hot wired it and it ran. no problems on the board we can see. Before buying another board is there another reason no power to the fuel pump load.
99 SKL

Followup from the Pelican Staff:

The fuse or fuse panel the power runs through could be faulty. I would remove the relay and check the feed to the relay. - Nick at Pelican Parts

Stan

January 10, 2017

Hi everybody,I need help! I have 1997 Mercedes c280,everything works,except fuel pump relay which is in the trunk doesn't get a signal to close a circuit,new pump and filter,checked all fuses and relays,please help

Followup from the Pelican Staff:

My suggestion is to get a wiring diagram, confirm the control side for the fuel pump relay is in fact at fault. It could be the DME or the wire itself. If the relay is manually activated, does the engine run? If so, it may just be the control circuit. - Nick at Pelican Parts

ChuckSnow

December 14, 2016

Hi there. My 98 C280 suddenly won't stay started. It will crank and then start, but dies within 2 seconds. Local garage said that it was getting fuel pressure, and basically gave up on trying to diagnose it. No codes. They think it is the key immboliser/eis system, but the eis is unlocking and engaging the starter. Thoughts?

Followup from the Pelican Staff:

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

Jimmy Bonz

November 16, 2016

got a 97Merc.320. Right Turn signal WON'T function.Left is Fine,Em.Flashers Work,all Bulbs checked and Good.Could Not hear relay Clicking at All for Right Signal???? HELP???

Followup from the Pelican Staff:

Check if the switch is activating the turn signal when it is on. I would grab a repair manual. It will have the wiring. Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts

Aida

November 9, 2016

I have a 1997 slk 230 and one of my fuses keeps burning out but I can't find the fuse box online. The dashboard lights come on when I turn the key but the car does not turn on.

Followup from the Pelican Staff:

Use your owner's manual to identify the fuses. if you don't have one, it should be available online.- Nick at Pelican Parts

Mark

November 2, 2016

Hi I have a 1999 SLK 230 I am having starting problems I turn the key to start the car all the dash lights come up but the engine will not turn over have checked the battery and its good for some reason the radiator fan starts running any advice on what might be the problem

Followup from the Pelican Staff:

is the starter getting the signal to turn on? Are there any fault codes stored? - Nick at Pelican Parts

euroguy

October 15, 2016

thanks nick for your quick answer, there is no codes ,and i will check next time for spark or the fuel system ,

Followup from the Pelican Staff:

Thanks for the follow up. We appreciate it. - Nick at Pelican Parts

Fiberjunkie

October 14, 2016

1999 E320 w210 4matic wagon dash key on function fine all dash lights. turn key to crank and one clunk no crank Start relay manually operated and cranks perfect but no ignition/run. Replaced EIS ESL and ECU matched set. no joy. checked every connection positive and negative, tried a K40 from running donor car still no joy! Stumped?!? whats the secret?

Followup from the Pelican Staff:

What fault codes are stored? Start may be blocked my immobilizer. - Nick at Pelican Parts

Gern2469

October 14, 2016

Just bought a 99 clk430. Bad ignition. Changed eis now it works properly cranks like mad and gets fuel pressure but won't start. Replaced crank and cam sensor k40 fuse box and relay. Only pending code is p1580 throttle acuator. Would the p1580 cause no start. Haven't checked spark but would think if one coil was bad it would still fire just misfire. Please any info would help. Ps was thinking maybe anti theft playing a part because ignition was broken.

Followup from the Pelican Staff:

Throttle fault will not block engine from starting, unless code is for mechanically jammed / open. Check spark, fuel injector pulse and (fuel pressure), volume, quality and engine compression. Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

euroguy

October 13, 2016

hello again ,i have a 2000 slk230 car stall on middle of the road and after 5 or more minutes starts without problems ,when this happens there is light on dash but not cranks,could be the k40 relay causing this problem? by the way secondary air injection monitor does not get ready for smog.

Followup from the Pelican Staff:

Possibly. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

SPIKE

October 9, 2016

Sorry should have added I didnt start car for over a month and the battery died,prior to this car was runnig great!
Thanks

Followup from the Pelican Staff:

OK, got it. - Nick at Pelican Parts

SPIKE

October 9, 2016

Hi,My Right hand drive SLK 230 Convertable starts and the engine runs but no acceleration when pedal pressed and the engine runs unevenly,MAF removed and no change,any ideas??Thanks

Followup from the Pelican Staff:

Is the check engine light on? Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders. If not misfire, look to see if the throttle is reacting correctly via TPS feedback when pressed. - Nick at Pelican Parts

Rich67

August 5, 2016

Thanks for the reply. It ended up being the MAF sensor. Ordered a bosch one from auto zone $120 compared to the dealers $600. Runs like a dream NOW.

Now it threw a map sensor code so I need to check the vacuum lines.

Followup from the Pelican Staff:

Thanks for the follow up. We appreciate it. - Nick at Pelican Parts

Rich67

August 1, 2016

Hello everyone. First time mercedes owner

So I just bought a 99 slk230 sport 5 speed from a 80 year old lady. In excellent condition. She barely drove it to the grocery store aND back the 12 years she owned it.
It starts right up sounds great no hesitations or stumbles revs up nice and smooth and fast. Idles perfect.

So I picked it up and the one problem it has is
When you accelerate more then 1/4 to 1/2 or more throttle DOES NOT matter the rpms it acts as if it goes into limp mode and then no more acceleration like loss of power.let off the gas and go back to under 1/2 throttle drIves great. No jerking no shakes nothing. It does try to still accelerate but acts like something is holding back.
Theres no check engine light on.
I changed spark plugs the y had Bosch supers. They looked like maybe original. Coil boots looked great no arc burns. Rubber felt soft not brittle. Coil wires looked the same

I took the MAF sensor off and it looked great no dirt or oil on it. I Still cleaned it with some MAF spray cleaner.

Neither one changed anything.

While test driving this time . I put the pedal to the floor and it seemed like it was trying to accelerate but the check engine light started flashing. I hurried and scanned it and read missfire 1 missfire 3 and random shut the car off looked at all connections started it up engine light was off and hasn't came back on.
But I haven't floored it yet either.

I then checked the supercharger to confirm it is engaging and as soon as I rev the motor it locks in and stays locked until it goes back down to idle. And then releases

I drove 10 miles freeway and streets driving it home from purchasing and it drove smooth, and great no missfires or hesitations, no roughness nothing.. IF IF I kept it under 1/2 throttle.

No engine light nothing.

Thanks in advance. Really appreciate the help

Followup from the Pelican Staff:

Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders. One of those items will be faulty. - Nick at Pelican Parts

Darlene

July 24, 2016

I just bought a 1998 SLK230 and it ran great for a day. When we went to start it last night all the lights come on, dash lights, windows work but it won't turn over. The battery is old so we switched out the battery. The batteries were dead on the remote so we switched out those. Still nothing. Any suggestions?

Followup from the Pelican Staff:

IF it won't crank the starter may be faulty. Voltage drop the battery cables, then check for the signal to the starter solenoid. - Nick at Pelican Parts

Defender

June 27, 2016

I have a UK RHD R170 SLK 230 with all the symptoms of a K40 relay fault engine cut out, LIM light on, fast engine fan but no engine crank. I took the K40 out and it had the same PCB issue as the one in your picture …solder joints on top LHS were burnt and the PCB discoloured. I took the PCB to a TV repair shop and they re-soldered the 3 insertions on the top LHS for £5, while I waited. Re-installed the K40 in the car ..and it runs perfectly. Interestingly, a top-end misfire and failure to kick-down on WOT now fixed too had been like that since I bought it 12 months ago. Just wanted to say THANK YOU for your website ..I wouldn't have got there without it!

Followup from the Pelican Staff:

Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community. - Nick at Pelican Parts

Nuxbantu

June 21, 2016

Hi Nick.Thanks for the detailed info, on checking the top left corner of the track I found 2 dry solder joint cracks. A pass with the iron and all is working as should be. Save a few quid on a replacement also..Thanks again

Followup from the Pelican Staff:

Thanks for the follow up. We appreciate it. - Nick at Pelican Parts

ChuckSLK320

June 16, 2016

I have a 2003 SLK 320, V-6 R170 6 speed. The car will crank fine for 3 or 4 days and then refuse to start. All the dash lights come on, but when you turn the key to the start position, nothing. Happens both when the car has been sitting and also being used. I replaced the clutch switch and used jumper cables to obtain another ground. When the car won't start the electric seat will not work either. Should I move on the K40 relay checked for bad soldier joint or some other problem. Could it also be the ignition switch?

Followup from the Pelican Staff:

I would check the signal to the starter. You if the signal is present when starting, the starter is faulty. - Nick at Pelican Parts

paulo

April 21, 2016


all cilinders at 10,5:1 compression, sparks checked ok, coils ok, fuel and air filter new, fuel pressure ok, no check light or any other indication, timming tensor replaced, ..... can you give me a hint? after a short time trying, as the engine warms up it idles rougthly and if you try to rev it up it ratters from intake....
thanks in advance

Followup from the Pelican Staff:

That is not a compression test result, that is the engine compression spec. Check engine compression. Spark and fuel injector pulse when cranking. I can't take a guess at a problem without some info as to what is going on with the engine. - Nick at Pelican Parts

paulo

April 17, 2016

Hi. i have an 1997 r170 manual 200 kompressor that was has this issue:
when you turn the ignition on it revs snothly for about 4/5 secs, then it starts working like it had only 2 cylinders and shuts down.
i have the timing tensor replaced, fuel pump, fuel filter, key imibilizer checked, coils and plugs, seted the motor to point and it stood the same. it starts very smoothly and 5 secs after it starts working like it had only 2 cylinders and shuts down. i called the mb road assistence and they only said that when it started stalking it had ignition issues on cylinder 2 or 3 and other times on 1 and 2.
de you think it might be an issue with the k40 relay? thanks

Followup from the Pelican Staff:

Is the check engine light on? Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders. Relay doesn't make sense for a misfire. - Nick at Pelican Parts

crayzhawyn

April 11, 2016

nick,
my k40 part number is 210 540 02 72 which has slight differences in pin locations and 2 less 15 amp fuses. I am getting fuel pump cycle and 50-56 PSI on the fuel rail. my question is; Does the K40 power the ECM/ECU K1 unit? When i had a diagnostic check on my Mercedes 96 E320 w210 M104.995 directly to the diagnostic connectorx11/40 the ECM/ECU was not one of the modules that showed up. Car turns wants to start but as mentioned fuel pressure is good but no pulse to a noid light on all injectors. I am stumped. FYI all new plugs and coil overs and boots were installed 2 1/2 months ago. Car stalled while overtaking going up hill then stalled, no restart. Changed crankshaft position sensor last week. didn't start after switch. disconnected battery to check fuel pressure and charge system when car restarted took for test run seemed fine , only unusual thing was my torque app would lose data feed intermittently. Next day I changed fuel pump and filter took for test and decided to test with same conditions as when stalled so i floored pedal and engine went completely off just like the first symptom. since then it has not restarted and battery is now depleted. Any help would be appreciated as I am un able to locate a matching ECM preprogrammed.

Followup from the Pelican Staff:

Do you have spark? if missing injector pulse, it can be a sensor input or a theft block. I don;t have wiring to look at for the relay you mentioned. - Nick at Pelican Parts

Matx

April 10, 2016

Hello, I own a SLK 230 year 1999.
Issue-1: the dashboard lights are on, stereo works but when I turn the key the engine is dead...no sounds at all that it wants to start.
Issue-2: Let's say I am driving in the city.. all of the sudden the car stops..then we go issue-1. Keep trying for awhile then it starts again.
my mechanic cannot find the fault .... would it be worth to replace the K40 anyways? or what other checks we can do? please help!!

Followup from the Pelican Staff:

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

Jude

April 7, 2016

Thank tou guys I love you guys for all. The dedicated work you the best help for foreign cars no others

Followup from the Pelican Staff:

Thanks for the feedback. Glad we could help. - Nick at Pelican Parts

Jude

April 6, 2016

Hello I have a 1999 slk the car cranks but won't start we recently replace the Sparks, coils , and fuel pump ... The car will only start on. Starter fluid and died I had a mechanic looked at it and he connected his battery on the fuel pump wind the car ran great but soon he takes the battery off it dies he said she the relay must not getting power to the pump because the car runs fine plus before all this car ran fine the we took a look at the relay it seems burn. On two joints but we unsure if it's the reason so I'm currently awaiting for a new k40 praying for the best
And idea to why the fuel pump not getting power And note the car at one point would blow this fuse every time we put it in the radio fuse but it stopped

Followup from the Pelican Staff:

Start with the relay. If faulty, it will not provide power to the fuel pump relay or fuel pump. - Nick at Pelican Parts

Sweeters

April 3, 2016

Hi I have a 1999 slk r170 which has developed a problem. Under acceleration it loses power but does not stall. It starts ok and appears to tick over normally. Any suggestions would be greatly appreciated.

Followup from the Pelican Staff:

Could be an issue with the fuel pump. I would perform a fuel delivery system test. Check fuel pressure, volume and quality. - Nick at Pelican Parts

Mikey

March 8, 2016

Horn not working, which fuse is it linked with? I cannot see it listed in any of the 3 fuses panel listings.
I checked the K40 and all looked good.

Followup from the Pelican Staff:

I don’t have that info. I would grab a repair manual. It will have the wiring and fuse info. Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts

Dgb

February 21, 2016

Nick I have 2000 230 SLK and it runs great and than I can be running down interstate or just iddling and the car just stops than want do anything when I turn the key. If I go and tap on the K40 it will start a do just fine. I replace the K40 and it did OK for a while...what could it be causing it

Followup from the Pelican Staff:

Tapping on the relay may have been a coincidence. The options of possible causes are endless. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

Mike

February 18, 2016

Could this cause my radiator fan to only turn on when the heating in the car is set to full with the EC off, its spins very weekly and the heater blower in the car works great?

I have a brand new fan control module which was the culprit at first and now about a month later the radiator fan is acting up again as mentioned above.

Thank you,
Mike

Followup from the Pelican Staff:

Have you checked if the fan power, ground or control signal is incorrect when the problem is present? That info can point you in the right direction. - Nick at Pelican Parts

Mysticfixit

February 12, 2016

Dear Nick, I've got a 1999 SLK Auto. It keeps popping the 2Nd. 15 Amp. fuse from the firewall K40 . I've searched high and low for what these fuses protect. I've opened the K40 & it seams to be OK. Please help. I thank you in advance.
Steve

Followup from the Pelican Staff:

I don't have wiring to check what is on the circuit. if you can get and share the wiring I can help. I would grab a repair manual. It will have the procedure, special tools and torque specs. Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts

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DRIZZY

February 7, 2016

THIS K40 DIAGRAM IS FOR THE OLDER K40 BOX CAN U OR DO U HAVE A DIADRAM OF THE 99 E430 DIAGRAM I NOT GETTING 12 VOLTS TO THE SIGNAL WIRE

Followup from the Pelican Staff:

I don’t have that info. I would grab a repair manual. It will have it. Give our parts specialists a call at 1-888-280-7799 - Nick at Pelican Parts

chippy

February 5, 2016

Just an update K40 relay repaired and working. It was the fuel pump relay inside the k40. 12volts going to relay but not activated. On close inspection the coil wire was slightly darker in colour than the other coils, it had burnt out on the inner wires but just showed slight discolouration on outer surface of the coil wire. continuity test showed fault. Replaced the fuel pump relay and working OK, Thanks to your detailed guide

Followup from the Pelican Staff:

Thanks for the follow up. Thanks for sharing your experience. These type of comments add so much to the Pelican tech community. - Nick at Pelican Parts

Iain

February 4, 2016

Does the k40 relay have anything to do with the roof ?operation wndows go down then nothing, if fault with swithes will windows still go down or does everthing need to check out first which might mean pump.do you have picures of elec connections for checking micro switches for front hood as you can check switches on hood at boot connection thanks Iain

Followup from the Pelican Staff:

What model and year vehicle? - Nick at Pelican Parts

chippy

February 3, 2016

Hello, My SLK 230 year 1999. Checking the K40 relay as per your great info guide. There is power at K40 relay to Red and Purple terminal. No power to fuel pump teminal yellow. All the solder joints look good. I connected all the leads back and removed the cover on the k40 so I could see the relays working as the engine was cranked. The relay connected to the yellow did not work but when I pushed the relay contact with a tooth pick the engine fired into life. removed toothpick and the engine dies.Is this a faulty K40 relay or should I be looking at other issues. Many Thanks

Followup from the Pelican Staff:

I don't have the wiring for the vehicle, so I can't be too much help on specific wire and terminals. Unless you can share a wiring diagram. The relay is not being activated. It may be the control for the relay. - Nick at Pelican Parts

olee

January 26, 2016

no fire to relay wire on k40

Followup from the Pelican Staff:

Trace the source backward to find the open. Use a wiring diagram. - Nick at Pelican Parts

Mac

January 23, 2016

Hi, I have a 1998 SLK 230 R170 right hand drive. When I turn the key to start it I get all dash lights as normal but it is just "clicking and not turning over. I'm an engineer myself so I thought this could be the battery. Checked the battery and it was fine. I then thought it would be the starter motor sticking. When's and got a new starter motor and fitted it on the side of the road but the fault is still there. I've seen people comment about a K40 or a K56 relay could this be the issue. Thanks in advance:

Followup from the Pelican Staff:

It could be. However, if you have a click the starter is attempting to engage. Voltage drop test the battery cables. - Nick at Pelican Parts

Tesla

January 16, 2016

I Ha this problem, the car would just stop all the lights would go out and the car would not restart for about 20 minutes. looked at the K40 board and all the solder joints seemed ok. but it did it again so I really got peeved off. using a soldering iron I reflowed every joint on the board.
Have not had the problem since

Followup from the Pelican Staff:

Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community. - Nick at Pelican Parts

Procam30

January 7, 2016

Thanks nick the dme is controlling the clutch on is not stuck , what its my problem what do I need to change , when the car is off no keys the clutch moves free turns by hand as soon I put the key on ignition turn the the key to position 2 engine off the clutch gets stuck , start the car the clutch it's turning never disengage

Followup from the Pelican Staff:

This could be normal for engine starting. There isn't room for guessing here. Using a Mercedes-Benz scan tool, monitor the actual and desired value for clutch control. Is it ON, what is the clutch state when the fault code is set? - Nick at Pelican Parts

Gio36

January 5, 2016

I found out what was wrong!! Nicked wires going to the ECU and the SAM

Followup from the Pelican Staff:

Thanks for the follow up. We appreciate it. - Nick at Pelican Parts

Amer

January 4, 2016

Hi Nick,
Our SLK 320/2001 is not starting! the fuel pump is not getting any power! the K40 seems to be ok with no burns or signs of damage including the fuses all good, but when starting the car the fuel pump relay is not getting activated! checking around on the net someone is saying that this problem might be caused by the fuel cut off switch but we are not able to locate the switch to check on it. can you please help with that.
thanks in advance

Followup from the Pelican Staff:

Before suspecting something other than the relay, does jumping the relay out allow the vehicle to start? Does the relay have power for the coil and pump? Is the DME activating the relay? - Nick at Pelican Parts

Procam30

January 4, 2016

Hi nick I have a 1999 slk 230 , manual transmission have error code p1236 supercharger clutch it's always engaged read a couple of forums and dicen red the conector for the supercharger and the clutch stops spinning then that's mean the clutch is not seized or burnt , checked my k40 relay it looks good no burns or bad solders any idea what it could be and why I need to do what I need to change or diagnose thanks for your time

Followup from the Pelican Staff:

is the DME commanding the clutch on, or is it stuck on? Check the signal to the control with the key on and engine off, then with the engine running. - Nick at Pelican Parts

Gio36A

January 2, 2016

Hello Nick,
I really looking for a help here:So my clk 500 wont crank wont start:Battery is good!When i tried to bypass the start relay the car cranks but wont start,i replaced the relayno crank no start.
i find out that there is no voltage to the purple wire from k40 to the solenoid,so i bypass it as well same resultcranking no start.
Please if you are having any idea, light me up.
Thank you.

Followup from the Pelican Staff:

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

muratti

November 26, 2015

...and if I cannot find the reason for the power problem, would it be safe to hook the fan to another swithed power supply inside the box with an additional fuse added to the circut? Thanks a lot. BR

Followup from the Pelican Staff:

Like mentioned earlier, sounds like the electrical unit you are pushing on is faulty. - Nick at Pelican Parts

muratti

November 25, 2015

Thank you Nick. I checked all the fuses. They are ok. Still no power to the fan. The car runs fine without problems. It is a 6 spd manual. Only when I push it hard, the left window stops working. Probably control unit is effected from exhaust heat. I need to solve the problem before the ecu is fried.

Followup from the Pelican Staff:

If physical pressure causes a change, the unit is faulty. - Nick at Pelican Parts

muratti

November 24, 2015

Hi Nick. I noticed that the ecu fan is not working. I checked with multimeter and there is no voltage on its cables when key is in pos 2 or the car is running. Fan is not seized and runs fine if you apply voltage outside the car. Is there a fuse related to this? Or can it be turned on/off through a menu when connected to a MB computer? Pls advice. Thank you

Followup from the Pelican Staff:

You didn't mention what vehicle you are working on. However, it should be fused, inside the E-box where the fan lives. Check for broken or corroded wires, as I have seen that in many MB models. - Nick at Pelican Parts

gregg

November 24, 2015

HI STAFF I HAVE 1999 SLK230 . when turning the key contact ON, it seems that dashboard lights are ON, and when getting the "bip" you turn the key to launch the starter but nothing happen, excepted that the cooler fan is activated, I wait a few minutes and the car starts . my horn dose not work could I be k40

Followup from the Pelican Staff:

It could be the relay. First confirm that the starter is not getting the start signal when the key is turned. Then trace that signal to the control side. You will find the loss of voltage. - Nick at Pelican Parts

Bob

November 19, 2015

Hi Nick. I had e check engine light and got a P1236 code. Checked my k40 relay but all was in good condition. After reading some more forum notes checked the turbo clutch and it was on all the time. I read the following in quotations and discovered that the clutch was OK but have a potential ECU problem. “If the clutch is constantly engaged, you can disconnect the 2 pin connector looks like a little barrel with 2 wires clipped to the engine and see if the clutch disengages. If this happens then you know the K40 is supplying power, the ECM is supplying ground or wire is grounding before the ECM and the clutch is not seized all in one shot.” Any suggestions on what to do next?

Followup from the Pelican Staff:

What vehicle are you working on? What did you do to confirm the turbo clutch is always on and how / where did you disconnect the control for it? - Nick at Pelican Parts

Et209

September 22, 2015

Hi Nick. Thanks for the quick reply. No check lights. Plugs are new and so are the coils. Strange is everything is good in the morning and I parked for work but sluggish when I am heading out for lunch! May consider doing a compression test too. Thx.

Followup from the Pelican Staff:

Check the fuel system when the problem is present. Possible the pump is failing. - Nick at Pelican Parts

Et209

September 22, 2015

Hi Nick, I have a 97 slk200. Car now runs fine in the morning but during the second part of the day and when engine is hot, it's sluggish and almost stalls when I lift off at the traffic light when I move from brake pedal to accelerator. Could this be a k40'issue, vacuum leak, throttle body? Any help is appreciated. I have changed fuel pump, cps, new coils and plugs, new MAF.

Followup from the Pelican Staff:

Could be a fuel delivery issue. Is the check engine light on? I would check spark, fuel and compression on all cylinders. - Nick at Pelican Parts

Gritz

September 8, 2015

When I check voltage in 40 amp fuse on the relay I get less than 3 volts

Does this mean a bad relay or power to relay broken Dow elsewhere

Followup from the Pelican Staff:

The relay may be the issue. Just confirm it has good power going to it. - Nick at Pelican Parts

brabus

August 25, 2015

Hi Nick.I just discoverd that when I start the car, it fires but it only revs when choked by hand at the inlet manifold but also refuses to idle.2there is also another component on my inlet manifold, held by 4 5mm allen bolts.checking current on this part reveals that there is no current flowing to it.could it be the cause? and what causes it to rev when chocked only? the red/green lights go when its revving.cant find anyone with a scanner tool since I stay in a remote place. :-

Followup from the Pelican Staff:

is the mass air flow connected? Are all the intake ducts sealed? - Nick at Pelican Parts

Walkrune

August 23, 2015

To be more concrete, symptoms include:
- when turning the key contact ON, it seems that dashboard lights are ON, and when getting the "bip" you turn the key to launch the starter but nothing happen, excepted that the cooler fan is activated. To note that the starter work correctly when launching manually, but engine doesn’t start.
Feedback of forums advises me to check K40 relay
What is your feeling on this problem? Your help will be welcome.
Thank you in advance
BR

Followup from the Pelican Staff:

The issue could be in the ignition switch or a control module. Get a wiring diagram and trace the starter solenoid signal from the ignition switch tot he starter. - Nick at Pelican Parts

Walkrune

August 23, 2015

Tanks a lot Nick. My 230 SLK is of 2001, automatic gearbox series. When you said that "the main relay module is activated...... air pump": this means that all 5 relays must be ON?
Best regards

Followup from the Pelican Staff:

Those are the relays that turn on when starting, according to wiring. - Nick at Pelican Parts

Brabus

August 20, 2015

Thanks a lot Nick.the mechanic checked everything and gave it a thumbs up.but still it cranks and fires after like 5turns, the revs go up to 2000rpm then suddenly it dies, like it does when one turns the ignition off then the red and green lights start flashing for some seconds,10secs or so then they go off.the mechanic says the immobiliser has armed but it has never had this problem.is it possible to remove this system.please help.

Followup from the Pelican Staff:

No, you can't remove immobilizer. There should be a code stored for start blocked by theft. Can you have the vehicle scanned for codes? - Nick at Pelican Parts

Walkrune

August 17, 2015

It seams that the problem on my SLK 230 comes from K40 relay. Nevertheless i would like to know which relays are ON when at the start?

Thank you in advance

Followup from the Pelican Staff:

I guessed at what year your car was for this info I am sharing. Take that into consideration when testing. The main relay module is activated, fuel pump, motor 87, traction, systems, horn and air pump. - Nick at Pelican Parts

Brabus

August 7, 2015

Hi.I have a problem with my mercedes 2001 w210 E320 petrol with the m104 engine.it had transmission problems and I bought a new tranny.so now the car starts and then dies right away.also the rear view mirror red and green lights start flashing.it didn't have this problem before the tranny was replaced.what could be the cause.your help would be greatly appreciated.

Followup from the Pelican Staff:

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts

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