Noisy main fuel pump.....one for the experts!!

Hi folks,

Well, my saga continues.....the car has stopped "kangarooing" (finally found a faulty fuel computer), but the main fuel pump is still noisy in my 1990 740GL B230F.

The mechanic is stumped.

Apparently, fuel pumps buzz loudly if they are overworked. Well, I have a new pre-pump & filter in the tank, a clean fuel filter, no obvious constrictions in the fuel lines, and full fuel delivery as indicated by a fuel pressure test at the front end.

I have put in a NEW main pump......which also buzzes <sigh>. Given the above.....what's left?? Faulty FPR? Faulty accumulator?? (Bear in mind I have full pressure as per specs).

Any ideas? The buzzing is loud at idle, and giving me a headache. The mechanic told me he has seen this before, replaced pump/s, without success.

Many thanks in advance,
Michael