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Holley 12-300 fuel pressure drop?

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  • 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
    That's normal fuel pressure drop after the 5 second Fuel Pump Prime time.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, forged steel crank & rods, forged pistons, Trick Flow T/W 11R 205 CNC comp ported heads, 12:1 comp ratio, 232-244 duration/.623" lift/114 LSA camshaft, TFS R-Series FTI comp ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM C6 converter, B&M Hammer shifter, Stifflers transmission crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.


    • #3
      Thanks for the info.


      • #4
        Does the fuel pump on the Holley 12-300 have a check valve?