My 1997 SL500 is encountering some starting problems, My "trusted" mechanic was seller and installer for a sprint booster (makes the throttle more touchy) for a lot of Mercedes models. He thought it would work on my car so we tried it out, it turns out that my throttle body/potentiometer (the part on the right side if looking at the engine bay under a plastic cover that controls the throttle position.) this part is was an older version. He wanted me to get a newer one off of an W211 or similar. So that was done and he installed the sprint booster and it worked! He did mention that it might cause a dead petal and to remedy this just restart the car. Now i KNOW this sounds awful but just keep reading haha. so he was half true on what he told me, when I started the car, it would be a random chance that it would actually start with everything working properly, when it would start it would have the ASR light on/ very prominent idle and also a dead petal. now when this would happen i would just have to cross my fingers and restart the car. this went on many many many times in one day and over the corse of like 4-6 months. after a while I would experience problems with my starter, as of now i have everything fixed with the engine and everything but just trouble starting. the car starts up fine, for a first start of the day. but if i drive it and park for 1.5 -2.5 hours and i try to start again, the starter will really really have to try to start and crank a couple of times and then it will finally start. HAHA it makes me look so bad. but if i park the car for 30 mins and start it, it will be fine. if i park it and start it after 3 hours it will start fine, it is just in the in-between area. I have been reading a couple of forums and i guess there is a number of parts that couple be causing this, anybody have any info? it would be much appreciated.

Note, I dont use that mechanic who thought this sprint booster anymore would be a good idea.

 

I would check to see if the crankshaft position sensor is sending a signal. The easiest way to do that is with an OBDII scanner that can read engine RPMs or with a Star Diagnosis PC.

 

I have this exact same issues. What was the cause in the end?