Hi,

I have a 1988 560SL with 109K miles on it which exhibits a problem starting on the first try if it is left to sit for 1-4 hours. Cold starts are fine and hot starts also are fine if restarted under 1 hour from shutdown. In the 1-4 hours range the car will sometimes seem like it is starting - the engine "catches" and revs up but then dies and will often start on the next try without incident. Sometimes it stumbles a little after that second try but will usually stay running and smooths out after 1-2 seconds.

I have replaced the fuel accumulator and check valve on the second fuel pump to eliminate the possibility of leak-down at the source, but that did not cure it. I've also replaced the coolant temp sensor. Any suggestions of what to try next would be appreciated. I don't have a fuel pressure gauge so if that's the next step I guess I have to buy one.

Thanks,

Marty

If you find out please let us know.

It is regarded as a common problem especially with the M103 6-cylinder.

Some suspect old fuel injectors leaking down.

Norm provides a great post regarding adjusting the EHA controller to compensate for age and possible vacuum leaks.

Checking that the Coolant Temp Sensor is in spec is another.

The easy fix is to give it a little throttle when starting under those conditions. Works for me and becomes second nature.

If the car is running well otherwise any other fix to the fuel system, pumps accumulator all seem to be irrelevant.

Good luck.

89 300CE
149k kms

Thanks for the reply. The temp sensor was the first part I replaced and that didn't fix it. I'll look at the EHA article and try the throttle open trick too, thanks!

-Marty

I found that replacing the fuel injectors, seals and holders as well as all of the air piping from the manifold up through the idle control valve to the injector manifolds cleared up my warm start problems as well as a slightly high idle speed problem I was seeing. Between leaky seal and leaking injectors I guess I needed to bite the bullet and replace it all and it worked!

1 long day under the hood and about $400 worth of part later and my SL is purring again.