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Thread: Fuel System Questions

  1. #1

    Cool Fuel System Questions

    Hello. I don't like getting spoon-fed info, but I can't find the answers I need in my searches.
    I plan on using a Holley 550-617 HP EFI Kit to control a 4.6L pulled from a Crown Vic and installed in my '64 F100.
    My issue is the fuel supply. The engine is from an '09, which (to the best of my research) had a variable fuel pump and a pressure sensor, not a regulator after the rails.
    Can the ECU vary fuel pump voltage, or do I have to switch to a regulator & return setup? Is there a recommended pump for either setup?
    Unfortunately, I'm 5600 nautical miles from home right now, so I can't go look at the engine to answer any questions you guys have. Really appreciate any help. -L

  2. #2
    Join Date
    Dec 2009


    I was curious about this to, so I emailed a Holley EFI engineer. This is his reply:
    "He needs a fuel pressure regulator. I’d just run a fuel pressure regulator BEFORE the fuel rails, that way he can use the stock fuel rails. He can use the in-tank Holley stuff with the regulator in the tank, and run a single fuel feed line to the engine."
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 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.

  3. #3


    Thanks for the help Danny, but I'm still kinda stuck. I called Holley support, and the gentleman on the phone recommended a Holley 526-7 Fuel System Kit. I have no issue running a regulator before the rails and a return, but this kit doesn't include a regulator. The rep said I need 45 psi at the rails, which matches some of my other sources.

    A drop-in unit would be easier, but the cost offset is significant. I also can't find any units that fit my tank. Finally, I may move the tank from inside the cab to under the bed in the future. These factors are leading me towards an inline pump mounted to a frame rail under the cab.

    So now my questions are:
    1) Can I just use an OEM regulator for a pre-2003 Crown Vic, mounted before the rails?
    2) The FPR requires manifold vacuum, correct? I'm concerned that because my engine wasn't equipped with an FPR, I might not have a port.
    3) Will I have issues mounting the pump lower than the tank? I'm concerned that the pump will have to draw fuel up, out of the tank. Thanks again.

  4. #4


    Alright, after more research, my current plan is to use an inline pump, and an adjustable fuel pressure regulator with a vacuum reference to the intake manifold.

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