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Thread: Fuel Pressure

  1. #11


    I’ll try that thanks. Had a Walbro 307, changed it and ever since I'm having that issue. I might put the old one to see it the new pump is the issue as the old pump always held pressure.
    Thanks guys.

  2. #12
    Join Date
    Jan 2010
    Brisbane, Australia


    Yes, the new pump has no check valve, and once it stops, the pressure bleeds back through the pump.
    Regards, Gary

  3. Default

    FWIW: I have in-tank Walbro 255 LPH (with Racetronix Turbo GN Sender) and it bleeds down after (Key-On/Engine-Off) pump prime. Not immediately to 0 psi, but slowly back down to 0 eventually in a matter of about 5 mins. Shoots right back up to 43 as soon as cranking starts, and never seen any issue from it. HTH

    HP EFI V4, 388cid Stealth Ram, 1000 CFM 58mm throttle body, Holley Dual Sync Distributor. LS Coil Near Plug, 1 bar MAP, 48 lb/hr Holley EFI injectors, 43 psi

  4. #14
    Join Date
    Dec 2009


    Yep, my Walbro fuel pressure happens the same way. It's completely normal.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

  5. #15


    My issue was a bad line from the pump to the sending unit in the tank.

  6. #16


    6.) Question: I’ve installed my new Aeromotive bypass regulator. Fuel pressure seems to adjust fine and holds great when the engine is running, but when I shut the engine off, pressure drops quickly to zero. Shouldn’t the pressure hold like it did with a stock regulator?
    Answer: No, Aeromotive EFI bypass regulators may not seal perfectly when the pump is off. They are engineered for the highest possible performance when the engine is running.
    Just an FYI if someone is reading this and has an aftermarket regulator. My MagnaFuel regulator behaves the same way. Annoying, but normal.

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