I posted last week about my 1990 740GLE stalling and not starting. I had both fuel pumps replaced which didn't resolve the issue. Members here suggested replacing the fuel pump relay which seemed to do the trick...a whole week with no issues.

When my mechanic replaced the main pump, the new pump made a very high pitched whine so he replaced that one figuring something was wrong with it. As mentioned above, I went this whole week with no issues but now, suddenly, today, the main pump is making the same high pitched whining noise! It seems to be starting and running OK but I am concerned as to why the noise has started.

Any thoughts or suggestions would be appreciated!

 

I have the same issue with my 740 sedan. The pump works just fine, the noise can get annoying if you have no radio though. I just think that if it breaks, then look into the problem. Other than that it should work just fine.

 

my main pump was noisy when the in-tank pump was failing. just because it was replaced, doesn't mean its working correctly (cheap aftermarket pumps have a moderately high dead-on-arrival rate, or maybe its a wiring problem or something). I'd disconnect the line from the tank to the main pump, hook a hose up into a big jug, and manually power the tank pump to verify its delivernig a steady stream of gas.

 

Are you sure it is the main pump vs. the in tank pump? I found that the replacement in tank pumps are noisier then the main pump . You can hear the tank pump from inside the car with the windows up where as I could not hear the main pump.