I own an '87 300E with 130K which has recently begun to stall unexpectedly after normal operating temp has been reached. It has never stalled when the engine is cold or is warming up, and has never been difficult to start when cold. It will always start again after several attempts and then will run fine (until the next episode). This happens maybe twice a day, usually in the afteroons with the AC on and the outside temp hot. I have replaced the fuel pump relay and the overvoltage protection relay in hopes of solving the problem, but it continues. Both fuel pumps and filter were replaced at about 100K. Distributer cap, rotor, coil, plugs were replaced within the last year. The battery seems fully charged. What could be going on here? Any thoughts would be appreciated. Thanks

Hmmm, could be the accumulator. Sounds a lot like vapor lock.

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Jeff L
1987 300e
1989 300e
1987 BMW 325

I was not aware that a running engine could develop vapor lock. If so, how could this be caused by the fuel accumulator, since the fuel pumps should be providing high pressure already?

I had a vehicle that would do the exact same thing and finally replaced the ignitor which resolved the problem. I do not know if this model has an ignitor or not.
engatwork

Sorry, I guess I misread your post. Hard starting is characteristic of vapor lock, but if it was running and the stalled or "died", it is not due to vapor lock, which occurs under high temp, low pressure conditions. Best diagnostic step is get the engine scoped and hooked up to computer to see if you can get any fault codes. Other possibilities are the fuel distributor, fuel pressure(yes it can be off even with new pumps), intermittent on the injection control relay.

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Jeff L
1987 300e
1989 300e
1987 BMW 325

Update and solution:

The engine continued to die while hot (usually in the middle of an intersection!) and eventually started stalling when warming up. Finally figured it out. With the engine running, I gently wiggled the fuel pump relay and the engine stopped. There were loose female connectors in the pin block. I then bent them back so they would connect tightly and the problem was solved. Hope this is of help to someone.

How, exactly, does heat impact a fuel pump relay? It is an area that does not get very hot at all.

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2001 E430 4matic
122,xxx miles
Black/Charcoal Interior

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Gone but not Forgotten:
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Engine compartment heat does effect the fuel relay most signifucantly. The fuel relay is notorious for poor or cracked solder joints. temperature... even a few degrees can cause metal to expand or contract and it only takes a thousands of a inch for a cracked solder joint to lose contact and shut off the fuel pump. Sometimes it's the pins but there is a high likelyhood that one of the little set of points that is mounted on the printed circuit board of the fuel relay has a crack in the solder that mounts it to the circuit board. These little guys vibrate (points opening and closing) and can cause a fatigue crack in the solder over time. Solution is to eyeball the pins of the little contact points where they are soldered onto the circuit board and then resolder the cracked joint.

I can say that it was probably not the pins being bent.... although that is a strong possibility... rather it is a broken solder joint on the relay 's printed circuit board. If the problem reoccurs... then its the solder... not a bent pin.
The cover will slip up and off the fuel relay to expose the circuit board.

Examine the back of the circuit board with a magnifying glass. If solder points are cracked then they will be visible. Solder cracks are usually circular around the pin and on the back of the circuit board.

I am almost certain that it is the fuel relay that is causing the problem If you can't fix it then purchase a new one from Parts shop.

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Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra