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Thread: No voltage on fuel pump blue wire.

  1. #1

    Default No voltage on fuel pump blue wire.

    I'm ready to start her up for the first time. It won't fire. I confirmed that it's getting the +12V signal. Shouldn't the blue fuel pump wire register +12 volts in the 'run' position? I don't hear the fuel pump run either when cycling the key. I did think it was the relay and changed it (the fuse is good too). Still no fuel. What else can I check?

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    19,253

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    Quote Originally Posted by wrager View Post
    Shouldn't the blue fuel pump wire register +12 volts in the 'run' position? I don't hear the fuel pump run either when cycling the key.
    Only during the fuel system prime time, 2.5 seconds after key-on. Then it runs the fuel pump again when the ECU receives an RPM signal.
    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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    Thanks Danny. Is there an RPM signal in the run position or only in cranking? Another question, I have the yellow tach wire joined to the existing yellow tach wire, 2 into 1 into the distributor. Any issue there?

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    19,253

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    Quote Originally Posted by wrager View Post
    Is there an RPM signal in the run position or only in cranking?
    Cranking & engine running; anytime the engine is rotating. There's no RPM signal key-on/engine-off.

    Another question, I have the yellow tach wire joined to the existing yellow tach wire, 2 into 1 into the distributor. Any issue there?
    I don't know anything about your ignition application (distributor, CDI box, etc.)? If you followed the instructions, it should be correct.
    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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    As I read it on another thread, did you complete the setup Wizard? The fuel pump won't prime before you complete the Wizard.

  6. #6

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    I did complete the setup Wizard process. The gauge readings all check out. When I cycle the key-on, no fuel pump prime. Oh, and it's a large cap HEI distributor.
    Last edited by wrager; 05-08-2017 at 05:00 PM.

  7. #7

    Default

    You can test the output of the blue wire with a test light or meter. But it may be easier to verify the pump has a good ground and actually runs by briefly applying power to it, since as mentioned the pump only runs for a few seconds at key-on. It also may take a while to prime the system if the lines are dry.
    Last edited by Zmann; 05-08-2017 at 05:45 PM.

  8. #8

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    After I installed my system, I connected the feed & return fuel lines together with a short piece of hose, and with male -6AN connectors on it and bypassed the entire TBI. I then took my portable jump box (any 12V battery will do), and removed the blue wire from the pump and powered up the pump from the battery in my jump box. The pump should run and you can check for leaks and all the feed & return lines. Not much pressure with this test, but at least this test basic fuel line integrity and proves the new fuel pump is working. I only had a few gallons of gas in the tank and I could actually hear the fuel returning into the tank. This process will fill the lines, soak the filters full, removing all trapped air. Then reconnect everything, turn the key, hear the prime and check for leaks again.

  9. #9

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    You can run the pump with it all hooked up to the Sniper for testing and getting fuel flow. It won't flood anything, that only happens if you key-on and boot the system, but don't start it a bunch of times and the prime shots start adding up. You can pull the fuel pump relay and apply 12V to the pump wire to test all the wiring.

  10. #10

    Default

    All great ideas! I will try that today. Thanks!
    UPDATE: Made some good progress today. After checking for continuity on the blue wire at various places, the fuel prime primes with key-on. Yay! But it won't start. I also checked for continuity on the tach wire at the harness plug, but I don't see it "sync" when attempting to start. I think I'll do a system reboot and go through the setup menu again.

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