My fuel pump buzzes a tiny bit when the gas gauge gets down to an 1/8th or so. Does this point towards a bad in-tank pump or clogged screen? Does changing the big filter before the main pump sometimes fix this problem? thanks

Usually a buzzing main pump is due to it being overstressed because of a non-functional transfer pump.

I have some info on a page of my website, take a look.

Greg Mustang
www.volvoclassic.bravehost.com

Also depending on where you live and level of rust on the underside of the car you may want to get the sending unit in case the one in the car is bad. The wire connections from outside to inside often fails due to rust and corrosion. Dan

Could be...

There are some great responses so far, but I'll throw in my two cents. My car exhibited some bad in-tank pump symptoms... and it sounded like the main pump would occasionally buzz.

After cleaning all of the main contacts in the engine bay the problems went away. I cleaned the FI and Ignition grounds on the engine, the engine ground strap, replaced the main 25amp LH fuse and holder, and the ring terminal on the battery to the LH-fuse. Nothing looked all that bad really, but it made a very noticeable difference.

May or may not be your problem...but worth checking out anyway.

-Ryan
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Athens, Ohio
1990 245 DL 130k M47, E-codes
1991 745 GL 280k (Girlfriend-mobile)
Buckeye Volvo Club

you could also have a working in tank fuel pump but a bad connecting hose inside the tank.

Don't know why nobody thought to mention that before - yes, if the little hose that connect the pump to the sender gets a hole in it, it will suck air when the tank is low, thus making the main pump work harder. Check that too, if you open up the tank.
--
Sean - now frolicking in the Land of a Thousand 240's (aka, Fredericksburg) thrice a week.

I have a '90 with the EXACT same symptom. I am not able to hear the intank prepump. I checked the voltage of the red/yellow wire at the wiring harness that leads through the bung nut (this supplies the power to the intank prepump). I had 13 volts with engine running, but there was no current draw at same wire. This indicates the the prepump is almost definitely dead. I say almost since there could be an electrical fault downstream from the wiring harness; e.g. at the prepump itself. The point of this story: check the voltage and the current draw before you buy a new prepump...there could be an electrical gremlin (or full blown Monster) that is preventing the prepump from working, e.g. fuel pump relay or fuse (#4 in a '90). There is a relevant post concercing this very issue back around October 25.

Good luck,

Charlie

i had the same symptom and was told that this is usual when the gas level is v.low and so long as the buzzing ceases on refilling the tank all is ok...
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Flame Trap UK

That may be true, but err on the side of caution - make sure the intank pump is working. If it's not, you could find your main pump dead one day, which is not exactly something you want to change on the side of the road for $200+.

It sounds like a failed in tank pump, open the gas cap and listen for the pump. If the pump is not working you are putting extra strain on the main pump and it needs to be fixed. Dan

Thanks for the replies. Is the in tank pump replacement a hard job? Does one really need the special bung wrench?

I've done it with out and it took me 10 times longer. For 25 bucks you have a tool that you can use for 25 plus years when ever you need to get into the gas tank. I just replaced a fuel sending unit with the tool and it was really not a job at all getting the bung nut off. It took me hours to get my first one off with out it.

I replaced my in-tank in less than an hour. 400,000km and Major corrosion. I had to beat the crap out of the bung (once i found the bung under all the corrosion). NO tool just a BFH and a brass punch. You have to be careful but it is not rocket science. If it looks bad consider buying new bung. Buzzing gone.

I replaced my in-tank in less than an hour. 400,000km and Major corrosion. I had to beat the crap out of the bung (once i found the bung under all the corrosion). NO tool just a BFH and a brass punch. You have to be careful but it is not roket science. If it looks bad consider buying new bung. I totally wrecked mine but its Volvo. I bent it straight and stuck it back on. Buzzing gone.