[Bschnell88]

So I bought a 2001 SLK 320 with 62k original miles this past summer and just haven't been able to get it running. The owner just had it inspected and everything a week prior and the car died on him so he let it go for a good deal. I fixed a majority of the other issues with it over the past few months and upgraded the headlights and grill. So I replaced the k40 box and still won't crank. I took apart the old k40 and turn the key and relay 3 and 2 close and a click noise comes from the top of the engine. I have taken the starter relay box out and jumped the starter with a wire to the battery and the engine starts right up. Seems like ignition is working if k40 relays are closing. I am at a loss on what to do next. Any help would be appreciated. Added a pictures of the day I got it since I would hate to junk such a beautiful car with low miles.

 

[Avel Du]

Did you get your K40 from Mercedes?

I ask because many members here have had issues form other suppliers ranging from short life, to not working at all.

 

[Avel Du]

These are threads from other members with similar issues.

Search results for query: no crank

www.slkworld.com

 

[BaD_81]

I have to ask close, engaged for a moment or kept engaged while the key is on pos ||?
As there is a difference.
In general mid 3 relays should close, but fuel pump needs to engage and "open" after certain pressure is reached.
Being 320, the K-40 and secondary air pump (not like mine) could have different logic/steps!
If the suggested searches doesn't help you can ask @M4rCu5 for any suggestions checking k-40 steps in 320s?

 

[Bschnell88]

Did you get your K40 from Mercedes?

I ask because many members here have had issues form other suppliers ranging from short life, to not working at all.

I did not. I ordered it online

 

[Avel Du]

If you have another member with an identical slk nearby you could try theirs and see before buying parts.

 

[Bschnell88]

I have to ask close, engaged for a moment or kept engaged while the key is on pos ||?
As there is a difference.
In general mid 3 relays should close, but fuel pump needs to engage and "open" after certain pressure is reached.
Being 320, the K-40 and secondary air pump (not like mine) could have different logic/steps!
If the suggested searches doesn't help you can ask @M4rCu5 for any suggestions checking k-40 steps in 320s?

They keep engaged. I pushed the horn relay together manually and it works, I push the fan relay and it reacts, and I push the other one which sounds like fuel pump and it engaged. When the key is engaged just the two engage and you were a loud click at top side of engine. I did notice I can't get the gas cap off the other day. I will say when I jump the starter the engine runs fine, but did notice my code reader can see the car when plugged into the obd II

 

[BaD_81]

The classic case with K-40 kaput is what you described.
No power to engine ECU = no communication with the diagnostics.
Another one is no power to Transmission Control Unit. And that will show no parking/neutral/gear position on the display next to the clock!
When you switch to pos || do you see the gearbox being in P or N? If not, you most likely have to dive into the wiring diagrams and check what is the pin you have to check in order to find 12V going to TCU!
But if you have not got genuine MB K-40 that is a match to your VIN, you are wasting time in chasing the wind.
All of the above is mentioned plenty of times in almost every K-40 involved discussion.
And yes we have PLENTY of them here.

 

[Dave2302]

Lets dispel some myths .................

The Car will have a 16 pin diagnostic socket, but it is not OBD compliant. Unless it has been on SDS and that doesn't communicate with ME2.8, then you can't draw any conclusions from using cheaper machines on these cars.

Secondly, we can discount K40 since the Cooling fan is not flat out and the Car starts and runs with starter hotwired, therfore the critical 2 relays in K40 are working, i.e. the ME Power Supply "Motor Relay" and the Fuel Pump Relay.

My best guess without some more details is on one of three items .................

Ignition switch

Pulse Module (NOT K40) pulse Module is underneath the Fuse Panel in the Underbonnet Fuse Box, opposite side of Car to the Battery !!

Wiring from ECU to Pulse Module

Question ........... Auto Trans or Manual ?

If Manual check Clutch Pedal Switch.

If Auto ....

Question .......... Does the Gear Display in ICM change when you move the Selector stick P, R, N etc

It could also be a fault with Auto transmission conductor plate as there is a Starter Inhibitor Microswitch in it. SDS can test all that in a heartbeat with live data, I do believe a Snap On machine will also check that data PID.

I do wish folks would refer to the Wiring diagrams, but seeings as I posted the 4 cylinder version of this picture earlier on in another thread here is the V6 diagram ................

Try these tests ....

First check Pin 1A has 12V + at all times regardless of Ignition Switch Position. Use a Test BULB rather than a multimeter, bulb must light brightly, do not use LED Type tester Multimeters and LED's can report false positive as there is no load. A 5W Bulb attached to a couple of wires is the daddy !!

Now check Pin 2B has 12V + with Ignition in Pos 2 and in Pos 3 (Cranking position)

Also check that 1B has a good 12V + supply with IGN Switch in Pos 3 (and Clutch Pedal depressed on Manual or Selector in P / N Auto), that will eliminate Clutch Switch / Auto Inhibitor !!

If those tests are OK now try this ....

Ignition Switch On in Pos 2, apply an EARTH via a bit of spare wire directly to pin 2A of the Pulse Module if it now cranks you have eliminated the Pulse Module.

 

[smsunder]

I highly recommend contacting the RCM/K40 guru, DJ Tighe who has rebuilt mine. His email is Tighed1 AT hot mail DOT com and he is located in AZ. His turnaround time fast and worth the $52.

nb link removed & address adjusted to avoid spam bots finding it. Remove spaces and replace 'AT' with '@' as well as 'DOT' with '.'

 

[Dave2302]

But this one is not K40 (based upon the info supplied) !!

 

[smsunder]

Based on year this would be the correct RCM from Mercedes which is the one I ordered and have a spare after DJ rebuilt the original unit https://www.amazon.com/gp/product/B07H3F6ZL9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[smsunder]

But this one is not K40 (based upon the info supplied) !!

Good catch! I posted the proper RCM

 

[Dave2302]

What I meant was the issue with this OP's car is not a duff K40 based on the info he supplied, i.e. it starts and runs fine if the stater motor is jumped !!

And I would not advise anyone to buy any K40 other than from the main dealership parts dept.

I could bore you with the details of all the DOA, failed in very short term and downright dangerous parts we reviewed and / or tested on fleets a few yers ago, but I won't because I'm too busy.

And those parts were actually being supplied by factors. And doesn't just apply to MB vehicles, we work on anything and everything

 

[2020SLC300]

So I bought a 2001 SLK 320 with 62k original miles this past summer and just haven't been able to get it running. The owner just had it inspected and everything a week prior and the car died on him so he let it go for a good deal. I fixed a majority of the other issues with it over the past few months and upgraded the headlights and grill. So I replaced the k40 box and still won't crank. I took apart the old k40 and turn the key and relay 3 and 2 close and a click noise comes from the top of the engine. I have taken the starter relay box out and jumped the starter with a wire to the battery and the engine starts right up. Seems like ignition is working if k40 relays are closing. I am at a loss on what to do next. Any help would be appreciated. Added a pictures of the day I got it since I would hate to junk such a beautiful car with low miles.

View attachment 624068

Nice SLK, paint looks exceptional. Thank goodness there are folks here that can help you with the technical. Though I would be much help there, I do know when I see a really cute dog!

 

[Bschnell88]

Lets dispel some myths .................

The Car will have a 16 pin diagnostic socket, but it is not OBD compliant. Unless it has been on SDS and that doesn't communicate with ME2.8, then you can't draw any conclusions from using cheaper machines on these cars.

Secondly, we can discount K40 since the Cooling fan is not flat out and the Car starts and runs with starter hotwired, therfore the critical 2 relays in K40 are working, i.e. the ME Power Supply "Motor Relay" and the Fuel Pump Relay.

My best guess without some more details is on one of three items .................

Ignition switch

Pulse Module (NOT K40) pulse Module is underneath the Fuse Panel in the Underbonnet Fuse Box, opposite side of Car to the Battery !!

Wiring from ECU to Pulse Module

Question ........... Auto Trans or Manual ?

If Manual check Clutch Pedal Switch.

If Auto ....

Question .......... Does the Gear Display in ICM change when you move the Selector stick P, R, N etc

It could also be a fault with Auto transmission conductor plate as there is a Starter Inhibitor Microswitch in it. SDS can test all that in a heartbeat with live data, I do believe a Snap On machine will also check that data PID.

I do wish folks would refer to the Wiring diagrams, but seeings as I posted the 4 cylinder version of this picture earlier on in another thread here is the V6 diagram ................

View attachment 624086

Try these tests ....

First check Pin 1A has 12V + at all times regardless of Ignition Switch Position. Use a Test BULB rather than a multimeter, bulb must light brightly, do not use LED Type tester Multimeters and LED's can report false positive as there is no load. A 5W Bulb attached to a couple of wires is the daddy !!

Now check Pin 2B has 12V + with Ignition in Pos 2 and in Pos 3 (Cranking position)

Also check that 1B has a good 12V + supply with IGN Switch in Pos 3 (and Clutch Pedal depressed on Manual or Selector in P / N Auto), that will eliminate Clutch Switch / Auto Inhibitor !!

If those tests are OK now try this ....

Ignition Switch On in Pos 2, apply an EARTH via a bit of spare wire directly to pin 2A of the Pulse Module if it now cranks you have eliminated the Pulse Module.

Thanks for this the car is an Auto and when I jump the starter from the wire that plugs into the pulse to the battery the car starts. Gear display works just fine. When I jump the starter I can drive the car just fine and shift the gears btw. I have some time to take your advice this week and work on it and report back. If the k40 is responding to the turn of the key don't you think the ignition switch is fine and maybe it is the pulse module?

 

[Dave2302]

If the k40 is responding to the turn of the key don't you think the ignition switch is fine and maybe it is the pulse module?

From what you have told me so far the Pulse Module is fine
From that Wiring diagram I posted in post #9

Ckt 15R (Ign Pos 1,2 and 3)

Ckt 15 (ign pos 2 only)

Ckt 50 (Cranking Pos)

Note that all at Ignition Switch are separate circuits, and all have 2 sets of contacts.

I am 99.9% certain your K40 is fine since it does start and run by hot wiring the Starter Solenoid, (but unless I was there with you fixing this I cannot be 100%)

I have had 2 exactly like this and both turned out to be a broken wire in the loom somewhere. I ran a new wire. I also do believe I helped another Member with this exact same fault and he had the broken wire issue.

You need to help me to help you by doing some of the digging

Find the SLK320 Wiring Diagrams which are on the R170 Forum, do your homework familiarising yourself with exactly what is involved between Ignition Switch, ME ECU, Pulse Module and Starter. Print and stick together the 3 Pages of the Engine Wiring, that will show details of the ME ECU's Power and Earth Connectors and Pins involved and they should be verified for power / earth !!
Follow the link in post #20 here

Wiring Diagrams for SLK230

This may have been answered in other posts but I can't find the answer. Are most of the schematics posted from the WIS module of the SDS? I assume they are, but how do you follow the wires and know what they are going to? example: S2/1 (ign switch) wire 4.0 15R PKYE goes to X4/18 then goes...

www.slkworld.com

You need a 5w Sidelight Bulb in holder or similar with 2-3 ft of wires attached, we are testing Power Circuits here, so Multimeters and LED Circuit Testers don't put enough load and can give false positive results due to small feedbacks from electronics on the Car.

Right now my money is on bad Ignition Switch or a bad wire between ME ECU and Pulse Module.

Here is a few tests to be going on with ..........

Use the light bulb tester to ascertain if you have 12V + at pin 1B of pulse module when in Cranking Pos 3

Again, same bulb tester, this time connect bulb to B+ and the other wire to Pin 2A of pulse module, (as the ME sends out an Earth to make Pulse Module engage the Starter Relay inside it) Does the test bulb light up in Ign Pos 3 ?

Which Pin are you powering at Pulse Mod ? I assume that would be Pin F ?

HTH