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Thread: Holley 12-300 fuel pressure drop?

  1. #1

    Default Holley 12-300 fuel pressure drop?

    I have the Holley 12-300 fuel pump module installed in a 1969 Camaro with an LS3 engine. I've hooked a fuel pressure gauge to the Schrader valve on the fuel rail. When I turn the ignition to on the fuel pump runs for about 5 seconds and the fuel pressure builds to 60 psi. Then after 5 to 10 seconds the pressure drops to about 45 to 50 psi. This is still before I start the engine. I've checked and there are no fuel leaks. I'm assuming this is not correct and that I have a faulty regulator on the 12-300. Before pulling the tank to replace the regulator, I thought I'd verify that the pressure should stay at 59.5 psi.

  2. #2
    Join Date
    Dec 2009


    That's normal fuel pressure drop after the 5 second Fuel Pump Prime time.

  3. #3


    Thanks for the info.

  4. #4


    Does the fuel pump on the Holley 12-300 have a check valve?

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