Ok, I know I should remove the RCM and clean it etc.. but I have an issue that someone may be able to solve:
I have issues with starting the car. It first turns over but will not start and the starter continues to engage even after the key is released, but again, does not start. So I turn the key all the way counter/ off which stops everything. I then turn full clock again and nothing happens.....then turn back full counter and start over and either get the same sequences or the car starts normally. Eventually the car always starts.
I read that only if the car does not turn over it's the RCM but I have not read about my scenario.
It could be a bad chip in the key? If so, the car will turn over and not start but continue to turn over even after key is released? And then turn key again and nothing?
Could be a combination of the two issues?
So clean, and or replace RCM and if still have issues, look at the key/chip situation?
Thanks.

 

If the car starts or attempts to start I doubt the trouble is the key.
The RCM could be bad, you could get a new one from Amazon and then send your original out to tighed1. You should have a spare RCM on hand anyway as well as a spare crankshaft position sensor (BOSCH only).
The starter sticking could also be a problem with the starter's "throw out bearing". That's the part that spins the flywheel to start your car. It could also be a bad ignition switch that is getting stuck in the "on" position.
These are all guesses. Without actually being in person and seeing what's going on, it's hard to diagnose the problem.
I would start with the RCM first though.
I've included some pictures of the RCM. It's located in the big box near the battery and is the closest to the engine.

 

The RCM is indeed the place to start. Get a new one and send your used to tighd1 for repairs/update.
Mercedes cars are programmed to continue the start sequence once initialized with the key in the start position; releasing the key the car will continue to turn over until the car starts. This is unlike American manufactured cars that will stop the starter engagement when the key is released from the start position.
If you have a problem with the start sequence "sticking"
the problem could also be in the pulse module which is located under the fuses in the fuse box on the driver side under the hood. There are two relays in there and as relays can stick or fail at their contact points it is a possibility that the pulse module is giving you trouble. USE the search box in the upper right corner to get more info on the pulse module should repair of the RCM not solve your problem.

 

Ok, that's what I was wondering, if this car is different than american cars and it keeps turning over until it starts....so that's like trying to start the car without the chip but of course it can be other things besides the chip as you mentioned.