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Noisy Main Fuel Pump, Dying? 700

posted by  Rtilghman on  Wed Jul 14 05:29 CST 2004
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1985 745t

Main pump has been making some noise latyely and I'm kinda wondering if something is wrong.

Quick rundown: Headed on a long trip across 90 (Wis./Minn./SD/WY) my main fuel pump started making some noise. Basically the pre-pump is known not working, but I didn't have a chance to change it out before I left. When I stopped for gas in SD I noticed that the main pump was making a little sputtering noise like air in the line or something, but it went away when I filled up and restarted. Since then its made more noises even when I have a full tank, though not quite as bad as the first time.

My question is if the pump is dying, or if there's another cause. When I've stopped to fill up I've noticed I get a big WHOOSH at the cap from the pressure difference. I imagine this is because I'm traveling very hot highways for long periods and the tank is steamy. Is the pressure difference a possible reason for the noises? Is it just the pump dying?

Thanks,
Rick








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    'Whoosh' of air when opening gas cap = vacuum from a poorly venting cap?? 700

    posted by  Allanwayne on  Wed Jul 14 08:27 CST 2004
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    last visit: Sun Jul 8 15:05 CST 2012
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    I may be wrong, but is the "whoosh" of air" when opening the gas cap not a sign that your gas cap is not venting properly and creating more and more vacuum in the tank as it empties? If so, both pumps will have to work harder to pump fuel against the vacuum. I was told to replace the gas cap once when this happened. Anyone else heard this as well??








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    Noisy Main Fuel Pump, Dying? 700

    posted by  Bean on  Wed Jul 14 07:47 CST 2004
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    last visit: Mon Aug 30 03:53 CST 2010
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    Probably need to replace both pumps.

    On a side note for future reference, my '94 945T had a noisy pump (like a constant, high pitched squeal) which was due to the Fuel Pressure Regulator failing. Swapped with a new one and all is well.

    How many miles on the car? I am thinking of doing a pre-emptive fuel pump change when my the 945T hits 150k. Anyone know if highway driving is easier on fuel pumps than stop and go? I'm thinking that it doesn't matter.

    Good luck,
    Bean
    --
    '80 242GT 92k, '94 945T 123k








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    Noisy Main Fuel Pump, Dying? 700

    posted by  someone claiming to be DannyMac on  Wed Jul 14 06:20 CST 2004 [RELATED]

    Sounds like it is dying. The non-working tank pump puts extra strain on the main pump. Probably need to change both soon. You might have a split hose on the in tank pump also. Considering the age I would replace all of the above.

    Good luck!
    DannyMac







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