Fuel pump diagnosis...

Discussion in 'GM Powertrain' started by alchemist1, Oct 5, 2009.

  1. alchemist1

    alchemist1 Member

    Just curious before I pull my fuel pump (which is consistently showing low pressure - 40-45 psi at test port at engine). Would the pump work at all if the voltage was low to the pump? I'm thinking what if I I had only 5-7 Volts instead of 12 at the grey wire? There's probably not a convenient disconnect to test this out?

    Also, will probably order the MU1748 AC Delco fuel pump/sending unit. Does it come with everything you need?
  2. mrmotorhead05

    mrmotorhead05 New Member

    The fuel pump is a DC motor so if you have low supply voltage, the pump wont spin as fast thus reducing the flow of fuel and thus cause low pressure at the engine. Just probe the insulation of the grey wire and check the voltage between him and ground with a volt meter, and you will find out if that is the issue. Happy hunting
  3. alchemist1

    alchemist1 Member

    Are you sure about this, that the pump would work with less than 12V? the bad thing about the 'grey'wire is that there's no connector convenient to probe. GM b-bodies have a long harness disconnect that is right at the rear bumper and you can disconnect and get voltage. Where's the best place to get to this grey wire (without dropping the daggone tank!!)?


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