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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Main fuel pump whiny humViews : 371 Replies : 4Users Viewing This Thread : |
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#1 |
New Member
Last Online: Mar 25th, 2024 14:01
Join Date: Dec 2017
Location: NC
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I've been hearing this strange, medium-high pitched hum on my 86 wagon for a couple weeks. Originally couldn't tell if it was coming from the dash or under the car. It's a constant pitch, dies a second after shutting off ignition. Lately it's gotten significantly louder. Car runs normal regardless.
Sticking my ear under the car and I'm pretty sure it's the main fuel pump. But is it whining because it is about to die, or because the in-tank pump is already dead? Today, I pulled fuse 11 while in idle and the sound got louder with a slightly higher pitch. I assume this means the in-tank pump is working properly and the main pump is about to go, but perhaps someone here might have a better suggestion. |
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#2 |
Go redblock or go home
Last Online: Yesterday 21:21
Join Date: Feb 2012
Location: UK
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It could also be a clogged up fuel filter, I'd try a filter first if it hasn't been done for a while and then if that doesn't improve things try a new pump, my 1990 760 turbo has the same thing, I've got a filter to fit to it but that's been in the shelf for over 12 months
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#3 |
New Member
Last Online: Mar 25th, 2024 14:01
Join Date: Dec 2017
Location: NC
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Could be, but if I'm replacing the filter, I might as well do the pump since they are both interconnected. I don't want to do all that and the real problem ending up being the in-tank pump or some other issue. I'm just seeing if anyone here can check my logic or suggest a better way to verify the issue.
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#4 |
Premier Member
Last Online: Apr 9th, 2024 21:44
Join Date: Jul 2009
Location: Holywood
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I would normally say a high pitch whine is expected. The fault condition I have seen is intermittent no start of the pump, while it gets more "grindy". But this was with the single intank pump. Basically these are unserviceable brushed motors and only last 100-200k Miles until the brushes wear out.
Whine getting louder seems unexpected to me. If its still working leave it alone, or if it done enough miles and you can get bargain replacements then do both. Maybe pull the pipes off and check you are getting flow from the tank pump. It might have already failed. Last edited by TonyS9; Apr 1st, 2024 at 14:37. |
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#5 |
SilverBrick Lives!
Last Online: Apr 27th, 2024 22:18
Join Date: Apr 2015
Location: Poynton, Cheshire
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My 940 with a single in-tank pump used to get noisier as the tank emptied, not sure if that is just the fuel damping the sound or it sucking air sometimes. It went for thousands of miles being noisy though.
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