Problems to start engine when hot. No problem when cold (below 80 degrees C)
 

Hallo,
I own a Mercedes C220 from 93. No engine modifications. Just had a service with change of air inlet filter and spark plugs
(150' Km service)

The problem is as follows :

When the engine is hot (over 80 degrees Celsius, it seems) it will not start by using the starter motor. However if i roll it down a hill, it will start fairly easy (sometimes it takes 5 revs or so). The normal runnig temp for the engine is about 85-90 Degrees Celsius.

The start motor runs the engine sufficient fast to start it when cold (starts actually very easy, maybe after 1 or 2 revs) and dosn't seem slow, compared to other cars.

If I let the the engine cool down a little (about 20 mins), it starts immediately by using the start motor.

I would appreciate help from anyone who has an idea what causes the problem !

Thanks in advance !

pfgjerpe,

Do you mean the starter will not turn the engine over at all when the engine is hot, or do you mean you can crank it with the starter and the car will not start and run?

If it is the first case, the starter acts like it is dead when the car is hot, you may have a worn out starter. Seems a little odd for your car, but it is more common on Diesels as they can frequently be abused, cranking too long and getting the stator windings (electrical coils in the stator) hot enough to damage the insulation on the wires. This damage is more apparent at higher temperatures and so when the engine says it is 80 degrees C, the area near the starter (on a Diesel it is near the exhaust manifold/pipe) can be much hotter. Since starters are used very intermittently, for short periods of time, they cannot be operated at their rated capacity continuously or they will overheat. If they were sized to run continuously they would be huge and heavy, so the solution exercised by automakers is practical and usually gives good starter life.

So, it sounds like you may need a new or remanufactured starter. Be sure you get one rebuilt by Bosch, not a local guy unless you are sure he will test the winding resistance with the stator hot. It is typical for Bosch to rewind Diesel starters when they are remanufactured. Good luck, and I hope this helps, Jim

Thank you very much for your answer Jim.

I am sorry that I did not express myself clear enough.
The starter motor runs fine, regardless if the engine is hot or not.

What I tried to explain was that when the engine is hot it will not start by using the starter motor (even though it cranks fine), but the strange thing is that it it starts (after about (5-6 revs) when I push-start it downhill. The latter situation may cause the engine to be run faster then the start motor manages, but I dont think that is the reason.

Any idea as to what can cause this problem ?
Electronic or mechanic ?
Any idea what to try to narrow down the problem ?

I would be grateful for any answer !

Hi check your fuel preuusre reg just put off vacuum hose at reg see if you can see or smell gas at reg vacuum fitting if yes replace the reg next thing to check is you over load relay. hope this help

Yes, I'd say OVP.

Thank you very much for your answer.

I will try the things that you mentioned in your mail, as soon as I can find the fuel pressure regulator.

Thanks again !

Paul

Just thought that I should post the solution in case other people should encounter the problem :

After a while the engine refused to start by starter motor even when cold, however it still started easily when pushed downhill (hot or cold)
The solution was that overload voltage releay was busted. Even though this releay has a fuse. In addition they changed the fuel filter. Now the motor starts every time very easy.

Regards to everyone who helped me

Paul

where is fuel pressure regulator on 190E?
 

I want to check this also but do not know where it is located. I have a 1993 190E 2.6 with similar problem. Before I go out to replace my OVP which is still stock, I want to check this also.

Thanks!