740 estate fuel pump noise

[AllHailKingVolvo]

Hi all,
Second Q of the day...sorry for the barrage of these!

My ‘91 740 has a noisy fuel pump-When running below half a tank, I get a swooshing noise in the cabin and audible fuel pump noise outside the car when running. It appears to be coming from the underbody pump rather than the in-tank unit.

It doesn’t seem to affect running (although the car seems less gutsy when close to 1/4 of a tank), but the noise is something I’d like to get rid of if poss.

Is the noise indicative of the underbody pump having to work harder as a result of the in-tank unit being weak, or is it just a case of changing the underbody pump to see off the noise?

The sound was present when I bought the car and hasn’t worsened, but it’s something I’ve been meaning to sort from the off.

Cheers
Phil

[Laird Scooby]

I'm sure you asked this a couple of weeks ago on another thread Phil?

First thing is narrow down which pump is making the noise, i'd hazard a guess it probably is the in-tank pump and the filter sock is partially blocked.

Possibly the pimp has to work harder when it's low on fuel as there isn't the head of pressure behind it, i know mine are noisier when it's low on fuel.

[Clan]

Originally Posted by AllHailKingVolvo

Hi all,
Second Q of the day...sorry for the barrage of these!

My ‘91 740 has a noisy fuel pump-When running below half a tank, I get a swooshing noise in the cabin and audible fuel pump noise outside the car when running. It appears to be coming from the underbody pump rather than the in-tank unit.

It doesn’t seem to affect running (although the car seems less gutsy when close to 1/4 of a tank), but the noise is something I’d like to get rid of if poss.

Is the noise indicative of the underbody pump having to work harder as a result of the in-tank unit being weak, or is it just a case of changing the underbody pump to see off the noise?

The sound was present when I bought the car and hasn’t worsened, but it’s something I’ve been meaning to sort from the off.

Cheers
Phil

The noise is air going through the main pump under the car , this will allow the pump to wear quicker as the rotor will be metal to metal with air bubbles going through . The problem is the in-tank pump not working for some reason ..

[AllHailKingVolvo]

Originally Posted by Laird Scooby

Possibly the pimp has to work harder

I’ll tell him...😂

[AllHailKingVolvo]

In all seriousness, thanks for your advice all. I’ll look at changing the in-tank pimp.

[Laird Scooby]

All i'm going to say is my typing isn't 100%!

Good luck with changing the in-tank pump, i've not changed the pump itself but have had the pump/sender unit out and refitted it, it's not a hard job as such, just a fiddle/faff to do.

Is yours a saloon or estate?