98 Volvo 7.4 LP fuel pump whine at idle

JoLin

Vice Admiral
Joined
Aug 18, 2007
Messages
5,146
Re: 98 Volvo 7.4 LP fuel pump whine at idle

Yeah, unfortunately I can't tell you how to test it (cover the air intake and stall the engine?), but it sounds to me as if your install oughta work the same way the OE pump did. Maybe one of the techs will chime in.

I'm going to think about your solution as those low pressure pumps sure seem to have issues. My last boat (5.7) whined for the 2 years I owned it, though the pump didn't fail. On the current boat, the pump on the port engine crapped out without any warning whatsoever. $200 for the factory part really hurts, in addition to the fact that it killed my day trip. Might be worth buying one and setting it up in advance so I can swap it in in a hurry if I need it.
 

GHfishin

Cadet
Joined
Jun 4, 2012
Messages
12
Re: 98 Volvo 7.4 LP fuel pump whine at idle

Thrird trip. Went over 100 miles round trip. burned 100 gallons of gas. still no issues with the pump.
 

oldboots

Recruit
Joined
Aug 28, 2013
Messages
2
We have been working on the same issues. Replaced 3pumps pick up tube, check valve etc,. Finally found by loosening gas cap the problem went away. Tightened cap and problem was back. Fuel fill is combination fill/vent. Hope this helps others.
 

jrwarrick

Recruit
Joined
Jul 31, 2014
Messages
4
oldboots...this is the second time I've read about people correcting the issue by loosening the gas/vent cap. Might be a silly question, but just how loose did you discover that it needs to be before it corrected the problem? My concern would be that vibrations from running the boat (engine and/or rough waves) might cause the cap to come too loose and fall out while underway. Are you merely suggesting to lightly hand-tighten it rather than use the "key" to wrench it down tightly?

Thanks in advance for answer.

John
 

jrwarrick

Recruit
Joined
Jul 31, 2014
Messages
4
oldboots...this is the second time I've read about people correcting the issue by loosening the gas/vent cap. Might be a silly question, but just how loose did you discover that it needs to be before it corrected the problem? My concern would be that vibrations from running the boat (engine and/or rough waves) might cause the cap to come too loose and fall out while underway. Are you merely suggesting to lightly hand-tighten it rather than use the "key" to wrench it down tightly?

Thanks in advance for your answer.

John
 

DCinVA

Seaman Apprentice
Joined
Jun 26, 2013
Messages
49
Old boats is saying that the tank vent is not working and needs to be repaired/corrected. Running your boat with the gas cap loose is not good idea. Loosening the gas cap was just a method to diagnose the issue. Fix your tank vents and you should be good to go.
 
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