I have a friend with a 99 E430. He takes very good care of it and has it regularly serviced. It is not his daily driver. His problem is that he can drive it for a while get out, shut it off. Then try to start it and all it will do is turn the engine over. He will have to wait awhile then it will fire up like no problem. He wants to try to isolate the problem without having a mechanic replace every sensor on it before he finds the correct one. Any help or input will be appreciated.

No service or check engine lights come on.

fuel pump?

No check engine light?  No codes?






 

I'm not positive with that particular model and I'm not a Mercedes mechanic,  but I have done some extensive work on them. My Mercedes Had a similar issue,  It turned out to be a bad cold start valve.

I work in an MB parts department.   My first guess would be the crank sensor.
 

just for giggles check that the gas cap is tight

Take it to a autozone and have them pull the codes.

Next take those code and google Mercedes E430 and the codes. Chances are there is a forum out there that will tell you what the problem is, how to test for it and how to fix it. That is what I do with my car.

One of the Mods in the car/bike forum is a MB tech..might wanna try there.