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Thread: Fuel Pressure Question

  1. #1
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    Cool Fuel Pressure Question

    I'm running my fuel pressure at 40 psi idle. How much should the regulator maintain at about 5k RPM?

  2. #2
    Join Date
    Nov 2013
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    Chicago IL
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    If it's a good regulator, working properly, you should see consistent fuel pressure regardless of RPM.
    If it's a boost reference regulator, you will see a rise with boost, and a drop with vacuum, that will be equal to manifold pressure changes.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  3. #3
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    Thanks, that's what I thought. My pressure is dropping to about 20 psi, then slowly picking back up. It's the regulator came with my injector set, and I really don't trust it. Next step is one from Holley, before I get into the fuel pump.

  4. #4
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    Quote Originally Posted by markvii91 View Post
    I'm running my fuel pressure at 40 psi idle.
    Ensure the fuel pressure is properly adjusted and the "Actual System Pressure" (Terminator - "Fuel Pres") is accurately entered in Engine Parameters.
    With TBI, the Actual System Pressure is measured anytime engine is running (no vacuum reference hose), or key-on/engine-off pump running.
    With MPFI, the Actual System Pressure is measured with the vacuum reference hose temporarily disconnected, or key-on/engine-off pump running.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 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, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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.

  5. #5
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    Thanks Danny. I've had problems keeping this regulator adjusted. I would set it and lock down the nut; and a couple of drive cycles later, it would sometimes increase or decrease pressure on it's own. I ordered a Holley 12-846 today. This should cure my problem. Thanks. Paul
    P.S. If it doesn't come from Holley or Summit - throw it back! Lots of junk look alike wannabes out there!

  6. #6
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    Quote Originally Posted by markvii91 View Post
    P.S. If it doesn't come from Holley or Summit - throw it back! Lots of junk look alike wannabes out there!
    I agree. Holley EFI products are high quality and have been very reliable for me.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 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, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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.

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