Occasionally, and more frequently as of late, the engine fails to re-start after sitting for a few minutes. I suspected the fuel pump circuit and validated this by attaching a switched buzzer to the relay that powers the fuel pump(under the rear seat). Using the buzzer, I can verify that the car is not started because power is not being supplied to the fuel pump relay. In normal function, the fuel pump runs when the key is turned on. Then, I think, once pressure is built up after a few seconds, the fuel pump shuts off. So there must be a pressure sensitive switch to cut power once a specific pressure is achieved. If the key is then turned to start, power is supplied to the relay and the fuel pump will run. Then obviously while the engine is running the fuel pump is always running. What reasons would the fuel pump relay not receive power while the engine is cranking?
Thanks for your help JB
99 E55 88 300E