240 1991 humming from fuel pump or sending unit?

Discussion in 'Volvo 240' started by jsegura525, Apr 8, 2007.

  1. jsegura525

    jsegura525 Guest

    Yesterday I noticed that there is a "new" humming/buzzing sound
    coming from behind the rear passenger seat area. I assume that
    it may either be the gas pump or sending unit? Is it getting ready to
    go out? Is the filter getting old/dirty and causing one of the above
    over work. Are either of these fairly easy to replace? How would I
    know which one to replace, should I do it soon or wait until the unit
    stops working or the buzzing drives me bats.
    jsegura525, Apr 8, 2007
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  2. jsegura525

    James Sweet Guest

    It's the fuel pump, there's nothing to hum in the sending unit. Does the
    humming go away when the tank is full? Usually what happens is the
    pre-pump in the tank or the hose connecting it fails and that causes
    cavitation in the main high pressure pump under the car which is the
    humming you hear. If this is not fixed, the expensive main pump will
    eventually fail. None of this is terribly hard to work on, if you can
    change a water pump you can change a fuel pump. Do it now, it would be
    silly to wait until it leaves you stranded, when the main pump fails
    you're suddenly dead in the water.
    James Sweet, Apr 8, 2007
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  3. jsegura525

    jsegura525 Guest

    Thank you for the reply....I have a couple of questions..please work
    with me here.
    The sound just started a couple of days ago, so I don't know if it
    hums on a full tank.
    I don't want to fill it up if I need to open it up to replace the pre-
    So as I understand there are two pumps, the main one is on the outside
    of the fuel
    tank, and a pre-pump inside the tank? When I replace the pre-pump I
    that I first off remove the fuel tank and then open it up and replace
    the pre-pump.
    How do I drain the fuel to make it easier.
    Thanks again for your help.
    Joseph Segura
    jsegura525, Apr 9, 2007
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