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

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


    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?

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

    I beleive all that info is there.
    Rob

    85 F250 4X2- 6.9/C6/3.55 Damn near all rebuilt. To much to list * 93 F250 SCab 4X2-7.3/SidewinderII/ZF5/3.55 * 93 F150 4x4-5.0/AOD
    And a couple of Subaru Outback's

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    Quote Originally Posted by nicksorenson View Post
    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?

    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.
    1985 F-350 repowered with a 1989 6BT CUMMINS

    THE DIESEL POWER UNIT UNDER YOUR HOOD IS AN ENGINE


    MOTORS ARE ELECTRIC

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