[ The fuel pump has an integral check valve assembly, and it is my belief the fuel pump check valve is the buzzing problem. When the check valve fails the pressure in the discharge line is not maintained and the pump runs nearly continually. Ours just failed and replacing it resulted in a three second or less zipping noise, followed by a lengthy shut off period. Even when running the check valve noise was very slight. I will dissect the old unit and check the valve guts out this weekend. Jim[/QUOTE]

Hi Jimsmith did you have time to dissec the fuel pump and the check valve? what is your conclusion? Any pictures?

I am interested to know the result. My car ( 260E 1988 EURO) has erratic stalling/loss of power since years.
Investing on faulty unit is always very helpful to all members to understand troubles

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Keep us posted especially if your problem is solved
Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class, 220CDI, 2009, W204

Sold: E-class 260E, 1988, W124, Wonderfull car sold after 489 000 kilometres of reliable services (engine M103, clutch, brake system and 5 speed manual gear box all original).

Sold: E-class, 320CDI, W210, 2000, 225 000km