86 325es restarting problem
 

The car has become unreliable by intermittently refusing to start again while still warm. Diagnosis seems impossible at this point since it will never fail when I try to troubleshoot. It starts fine after sitting overnight. So far, I have replaced only the main relay, but that was, apparently, not the problem.

Has anyone had similar issues and been able to resolve them without buying a new car?

Does your MY have a fuel accumulator in the fuel run from the tank after the pump??

If so, when they go bad, they can cause a bad warm start issue...

All I can think of right now.

The other thing that comes to mind with a warm restart problem is the water temperature sensor that talks to the fuel control computer.

When the car is hot but won't start does the starter function properly? Does it turn over?

It's common that a car with a failing starter will start fine when cold but wont start when warm. Why? the wires in the starter winding heat up and cause open circuits as they expand when they cool they shrink and function.

Thank you all for these suggestions. Since the starter turns the engine over even when hot, I'll rule that out for now. I'll look at the fuel accumulator and water temp sensor and let you know what I find.

Best regards.

John

Fuel Pressure regulator could letting too much return to tank.

Check the coolant temp sensor in the themostat housing.

These cars dont have fuel accumulators. There is a slim chance that the fuel pressure regulator may be going out as well.

I have replaced the coolant temperature sensor in the thermostat housing with no change to the problem.

A new fuel pressure regulator is on order, should arrive anytime. I'll post results.

It has also been suggested elsewhere that the air-flow sensor may need adjusting. Any comments on this one?

Meanwhile, thanks for everyone's interest and help; keep those cards and letters coming in.

Well, so much for the fuel pressure regulator being faulty.

At this point I've decided to take it to a Bimmer specialist who has diagnostic equipment. I've tried the built-in diagnostic system of pedal pumps and flashing "check engine" light codes, but I must not be doing that correctly. I think the Germans who invented the Enigma code machine during WWII had a hand in this code as well.