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Thread: Fuel Pump Prime

  1. #1

    Default Fuel Pump Prime

    Will increasing the fuel pump prime make it crank easier? What do most of you have yours set at? I have a 302, mild cam, it's got the Sniper EFI on it.

  2. #2
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    Quote Originally Posted by Road_block View Post
    Will increasing the fuel pump prime make it crank easier?
    I suppose if it optimizes the "cranking air/fuel ratio", it'll crank faster to start.

    What do most of you have yours set at?
    If you're referring to the "Fuel Prime Percent", 150-200% is usually good for big blocks, and 100-150% is usually good for small blocks.
    http://documents.holley.com/techlibrary_199r11259.pdf (Holley Sniper EFI Help Manual - EFI Software, Tuning & Datalogging)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

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    OK I'll try less first. Might be too much at 150%, if 100-150% is better for small blocks. Better less and not flood it, than too much and flood it right?

  4. #4
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    I doubt you're actually "flooding" the engine with fuel.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

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    Startup Settings - Enable Fuel Prime
    Description: For MPFI applications, the system will inject a single pulse of fuel, after the first crank pulse is detected. This will only re-occur after an engine starts. Above this value, no fuel will be injected when the engine is cranking/starting. For TBI applications, the system will inject a single pulse of fuel when the key turns on to wet the intake manifold. This will only re-occur, after an engine has started. If you cycle the ignition key multiple times, it will only perform the first prime.
    Startup Settings – Fuel Prime Percent

    Description: The “Fuel Prime Percent” is a multiplier that works off the “Cranking Fuel” Value in the Startup Enrichment table. The pulse width of the single shot of fuel prime fuel is based off the Cranking Fuel value (which is temperature based) and multiplied by the “Fuel Prime Percent”. A starting value of 200% is usually a good point for MPFI engines and 50% for TBI applications.
    I had mine at 5% and it seemed to dump way too much fuel, I turned it off completely, and rely on Cranking Fuel. I reach in and turn the key and it starts pretty easily. One of the things I seemed to get right. Mine is a little more radical 548 BBC. I guess it depends on the combination. Mine is multi-port, TBI might be different, like it says wet the TBI intake.

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