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Hi all,

I have a 98 SLK which has done a fair few miles, but generally works well.

Yesterday driving locally - the engine suddenly cut out, and the starter wouldnt work - nothing at all.

Electrically all seems fine, the engine fan comes on when I turn the ignition and all warning lights display as normal. There are no warning lights staying on etc.

Nothing at all from the starter motor.

Looking round the forums suggestions point to the K40 relay and CPS - I can replace these - but wondered if the above sounded like it could be caused by either/both of these.
 

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Premium Member 2001 SLK320/2000 SLK230
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If the starter motor is never engaging it is probably not the CPS. Any warnings displaying or codes ? If nada the first thing I'd do is to pull the positive battery terminal for about a half hour and try again. If it is just confused this may work and is free. If that does not work we can go deeper.
 

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Registered 1999 SLK230
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Hi all,

I have a 98 SLK which has done a fair few miles, but generally works well.

Yesterday driving locally - the engine suddenly cut out, and the starter wouldnt work - nothing at all.

Electrically all seems fine, the engine fan comes on when I turn the ignition and all warning lights display as normal. There are no warning lights staying on etc.

Nothing at all from the starter motor.

Looking round the forums suggestions point to the K40 relay and CPS - I can replace these - but wondered if the above sounded like it could be caused by either/both of these.
Sounds like when my K40 relay failed. Did the engine just die when driving, or would it not start? All electrics seem OK and no starter?
 

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Discussion Starter #5
That's exacty it. Engine died while driving, and then wont restart. All other electrics are fine.

I've pulled the K40 board. There are MB relays on the board which all look OK, one has slightly burnt looking solder joints.

There is also a 'custom' relay soldered in position 1 on the board (furthest away from the orange 40Amp fuse). This looks OK but most of the K40 pictures I've seen only have 4 relays.

I'm going to refresh all the joints with solder and see if that helps. I'd like to test the relays - persume 12v is required plus identifying the correct terminals.
 

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Discussion Starter #6
Thought I'd update on my engine cut out.

So after looking through the forums, I removed the K40 relay module and resoldered all the joints. There was a slightly dodgy looking relay but testing it manually with a PSU, all seemed OK.

I put the module back in - and still no joy.

Tried replacing a couple of the relays with new ones - still no joy.

Finally - I purchased a new module from a Mercedes dealer and installed.

It now works!

No idea what the issue was with the old module, but glad the new one works OK.

FYI - my failure ocurred during driving. The engine just cut out and that was it. The engine never fired again with the old module despite numerous attempts. There were a couple of things I noticed after the failure - no fuel pump sound when you turn the ignition key, and the radiator fan on full speed.
 
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