How do I know if my Fuel pump (lift pump) is bad?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by nicksorenson, Oct 2, 2007.

  1. nicksorenson

    nicksorenson Full Access Member

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    How do I know if the lift pump is bad? Will the truck run/miss/rattle make a clunking noise etc?? Also, what are signs of the injection pump going out?
     
  2. f-two-fiddy

    f-two-fiddy Registered User

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    The FAQ's, above, are a good place to start.

    I beleive all that info is there.
     
  3. MIDNIGHT RIDER

    MIDNIGHT RIDER Full Access Member

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    Before doing anything else, install a mechanical fuel-pressure gauge, between the fuel-filter and injection-pump; even better, use two, one where already suggested, and a second one just ahead of the lift-pump.

    With a reasonable clean fuel-filter, and a factory-type diaphragm lift-pump, the rotary injection-pump, like on the 6.9/7.3, should be able to draw enough fuel through a completely dead lift-pump to run the engine.

    The trouble is, running in this manner, the injection-pump will be starved of vast amount of cooling/lubricating fuel that cycles through the return-lines.

    Running with a dead lift-pump has been the demise of many injection-pumps.

    Then, when the injection-pump quits, someone will replace it, while not giving a thought to the lift-pump, and the cycle goes on.

    Without a gauge, you can remove the fuel line, ahead of the filter, and have someone crank over the engine, while you aim the fuel-line into a jug.

    If the pump is good, it should throw a strong gusher of fuel.

    A healthy diaphragm pump only holds about 7 PSI.
     

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