W209 CLK320 starting issue

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New Member
May 24, 2021
2003 CLK320
Hi all,

I have an intermittent starting issue with my '03 CLK320.

About 25% of the time, when I turn the key to start the car, all the "position 2" stuff happens like normal (the steering lock comes off, the dash powers up, the seatbelts come out etc.) but when I turn it to position 3 to start the car, the engine doesn't crank or it cranks for a millisecond - almost imperceptibly. If I hold the key in this position it will often crank totally fine and start a few seconds later, or sometimes won releasing the key it will then crank and start. Even rarer still I have to turn it all the way off and then try again. So far it has always started after one or two goes.

So far, I have charged and 'reconditioned' the battery (which shows healthy readings), changed the battery in the key, changed the starter relay.

From the searches I have done so far, this doesn't look like a common set of symptoms. No warning lights are shown and no codes are stored. The tacho doesn't show any revs when it refuses to crank.

Does anyone have any thoughts on what I should try next, or what the problem may be? Any help appreciated.
Thanks for the reply.

I would assume the starter motor might show different symptoms, but I could be wrong. The issue definitely feels electronic as the car starts perfectly when it actually cranks.

I took the key to pieces yesterday and contact cleaned it all. So far 3 restarts with no issue, but I would be staggered if that really was the fix. EIS looks most likely, but I don't want to just throw parts at it without a high level of confidence that it will resolve the problem.
The problem you describe is unfortunately nigh on impossible to diagnose over the web, without experiencing the symptoms first hand. When a starter begins to fail, it generally start with the solenoid sticking and requiring a few tries to get it to engage. The EIS is of course unfortunately the most likely culprit though, I agree.
You can take out your current EIS and get it copied to another used EIS. I have done this in the past when I was trying to diagnose a starting problem with my car.
Have you solved this issues. Mine is doing what you’ve explained and I’m lost. Had the key module looked at and it was fine!
A very old issue with these were that the ring gear and starter motor gear needed lubrication. The exact symptom it turns for maybe half a second then stops.
Thank you BlackC55, however, I don’t think it will be this as when it does try, the starter does engage to the engine. It turns over in very short bursts, or continues to crank without firing, or it doesn’t do anything at all apart from dash lights and fuel pumps. Other times it starts just fine.

I believe it may have been the blocked water drains in the roof and scuttle panel. The A pillar and floor on the drivers side was wet. I’ve cleaned these out and also dried everything out. It’s been as good as for just over a week, but then done it once after.

Are there any modules or plug connections in the footwell or under the scuttle panel that could have got wet?

Someone please help as nothing is showing up in star and it’s doing my head in!

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