[visionhawk]

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

 

[seancutler24]

how many volts to the pump

 

[visionhawk]

You may well be on the right track.....

Hi Seancutler24,

Since my post I stumbled on a wonderful article online about all the myriad hassles with Volvo relays.....especially 10+ year old ones. Apparently manufacturers use a different solder to the electronics people, and it crystallises with age. Ergo dry solder joints and infuriatingly intermittent symptoms.

I am guessing that your question is leading to the relay? If so, well done, as I made a number of enquiries, and the last being a Bosch fellow, who said 'yes, incorrect voltage at the main pump will cause cavitation & therefore buzzing'.

So tomorrow I am going to take a new one to the mechanic and see if that finally puts everything to bed. It may also fix a very slight hesitation at highway speed (100kph)..... I have my fingers crossed.

So I give you a big thank you in anticipation!

 

[visionhawk]

Link to very interesting site of Volvo info.....

This site has some great information.....even how to repair my 740 odometer!


Volvo Relays

 

[visionhawk]

Follow-up on relay.....

Unfortunately a new fuel pump relay did not do the trick....still buzzing. Running out of things to check.....anyone have any ideas??

 

[BHart]

Is this an external fuel pump? Have you used the proper rubber mounts? Are things too tight or is a fuel line re-mounted tightly to the body.

You may just now be more aware of the noise.....

 

[StephenC]

In regards to the noisy fuel pump, Some fuel pumps can be noisy for a few different reasons. 1. If the fuel filter is plugged it can make the pump noisy. 2. If the fuel pump is in the tank incorrectly to were the pump can touch metal in the tank to make noise. 3. The fuel pump assembly is giving you signs that it is about to fail and needs replacing. Hope it helps