My 1997 E300 (137,000 miles) stalls while running normally. It can be on the highway at 50 mph, or a side street at 5 mph. The engine just stops. I coast to the side of the road and try to restart it. After several tries over a minute or two, it will start up and run perfectly. It will continue to run fine sometimes for several days, and sometimes for longer before stalling out again.

I notice when it won't restart that the preheat lamp will go out immediately (or not come on at all sometimes) instead of hesitating for a fraction of a second as it usually does with a warm engine when turning the key.

It seems to me that the problem must be in a circuit that controls the fuel and also the preheat, as the preheat indicator doesn't show proper glow plug operation when the car won't start. I can always tell when the engine is ready to run again when I turn the key and the preheat lamp comes on again.

Thank you.

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rhack