Hi, I hope all are well.

The main fuel-pump on my 1985 245ti makes an abnormal loud high-pitched buzz (African killer-bee-like), sometimes almost grinding noise. I'll look into it further when I find the time. The car is new to me, not yet legally on the road but runs mostly well during 'test-runs'.

This evening, though, I laid down besides the parked, running car and pinched the fuel line, along a 12 inches length, just before it goes into the pump. I wanted to see if I could feel air bubbles that might be coming from the in-tank pump (I think I did feel some).

To my surprise, after some pinching of the fuel-line, the main pump would become quiet for 15-20 seconds at a time. No more African killer-bee-like loud buzzing.

Does anyone know what such a phenomenon might imply, diagnosis-wise, for the overly loud main fuel-pump?

Thanks in advance ( and in retrospect...)

Read my saga a few posts down from yours.

I should be a real expert at this. I've had the in tank pump out about a dozen times and the main pump out five or six times over two episodes already. Like yourself, I have pinched the supply line to the main pump and heard quieting in dismay.

From my experience, when the main pump is noisy, the problem has always been the pre-pump and has never been the main pump.

I think I got a bad prepump out of the box in one episode and that made me go off track and do the 740T pump upgrade thing. That lasted a few years until a piece of plastic got stuck in the impeller.

Here's what I'd do. Prepumps are cheaper than main pumps. If you're going to guess without pulling the bung off the tank, start there. I've actually bench tested them, though you've got to be careful of sparks and don't run them more than a few seconds in open air so they don't overheat. Plunk down your $160 on a main pump as a last resort. Or jerk one from a boneyard.

Just my .002


--
Volvo Farmer:

21 Volvos '58-'91

445-544-122-144-1800-240-740

sorry, no FWD

Bob, I'll be pulling the in-tank pump to check it out. I suspect a split fuel-line on that pump. Thanks for sharing!