Results 1 to 2 of 2

Thread: No start unless power is ran to the green fuel pump wire.

  1. #1

    Default No start unless power is ran to the green fuel pump wire.

    I've changed the fuse near the relay, but my engine will only start if I feed power to the green fuel pump output wire. What am I missing?

  2. #2
    Join Date
    Dec 2009


    Quote Originally Posted by LSX55 View Post
    I've changed the fuse near the relay, but my engine will only start if I feed power to the green fuel pump output wire. What am I missing?
    Fused +12V & Switched +12V:
    Since the fuse is fine, I'd start troubleshooting the system relay. Have you performed a TPS Autoset?
    Also, ensure the Switched +12V red/white wire (pink wire - Sniper EFI) is powered in the "Run" and "Crank" key positions.
    The ignition switch must have a wire that's powered in "run" and "crank" key positions leading to the ignition system.
    The ignition switch can't start the engine, if there isn't a circuit that's powered in the "Run" and "Crank" key positions.
    The easiest way to find this wire, is to look at the wiring schematics in a factory shop manual or even a Haynes manual. (MSD Troubleshooting - Engine Run-On) (Scroll down to "Typical No-Start Checks".)

    System Relay Troubleshooting:
    Troubleshoot the system relay & its wiring. The system relay's coil is grounded at terminal #85 by the loose black wire.
    The ECU's J1A-A2, (22 AWG red wire) energizes +12V the system relay coil at terminal #86,
    during the 5 second Fuel Pump Prime time, when cranking, and when the engine is running.
    There's a fuse next to the system relay, that powers the relay (14 AWG red wire) at terminal #87.
    The system relay activates the fuel pump, and powers the fuel injectors (& ignition coils - LSx, MOD & HEMI) from terminal #30.
    The ECU pulses the ground side of the injectors to spray fuel. Which of the above actions isn't happening? (Holley EFI Wiring Manual - Sections 2.1 "Pin-Outs" & 13.0 "Wiring Appendix") ("Test Relay" for troubleshooting/diagnosis.)

    Injector Wiring Troubleshooting:
    You can use an injector noid light (LINK), an injector probe (LINK), or even a long screwdriver used as a stethoscope (placed between
    an injector and your ear, listening to each working injector). Ensure the spark plugs aren't fuel saturated and therefore won't fire.
    An injector noid light only indicates if the circuit is active or dead; it's just a convenient (quick connect) test light.
    It doesn't indicate if the +12V or Ground pulse is the problem; you'll need a multimeter (volts) to determine this.
    If you're working alone, use a remote starter switch (LINK) to jump the starter and crank the engine (key-on).
    To check for constant +12V while cranking, connect the positive multimeter probe on the injector connector +12V pin, and the negative multimeter probe on battery −.
    To check for pulsed Ground while cranking, connect the negative multimeter probe on the injector connector ground pin, and the positive multimeter probe on battery +.
    Another possibility, is if one of the fuel injectors is shorted out and incapacitating the ECU's injector drivers. Try unplugging all fuel injectors and test one connector. (Holley EFI Wiring Manual - Section 13 "Wiring Appendix", Figure 18, Page 31) (ECU/Main Power Harness Troubleshooting Post)

    Originally Posted by Danny Cabral
    EFI Software Problems:
    Often times, when EFI software related functions don't work properly, it's caused by a corrupted software download/installation.
    I suggest completely removing the Holley EFI software from the "Control Panel", "My Documents" (Holley folder) and the
    "C:Drive" (Program Files, Holley folder) and install a fresh EFI software download. Save your Global Folder somewhere.
    ECU Firmware Problems:
    Conversely, often times, when actual ECU related functions don't work properly, it's caused by a corrupted ECU firmware installation.
    As a last resort, you can try reflashing the ECU firmware version (LINK). The ECU firmware is in with the software download (LINK).
    Also, try completely disconnecting the battery for 20 minutes. This "resets" some unusual ECU issues.
    Originally Posted by Danny Cabral
    Crank & Cam Sensor Wiring Tips:
    The 10-pin Ignition Connector has one "Chassis Ground" (loose black wire ground) and two "IPU Grounds" (clean ECU ground).
    Don't use "Chassis Ground" to ground an ignition module (or crank & cam sensors). It's quick & easy to move the ignition
    module ground wire from (cavity) pin D "Chassis Ground" to pin C or G "IPU Ground", where it should be.

    If you don't have the actual Metri-Pack terminal release tool, a "safety pin" will work.
    It just needs to be a stiff wire between .030"-.035" in diameter to release the terminal tab.
    Then reopen (bend) the terminal tab before reinsertion, so it will clip (lock) into the cavity. (T-6 Micro Terminal Release Pick Tool)

    Also, don't use (cavity) pin E "Switched +12V" from the 10-pin Ignition Connector, to power an ignition module
    (or crank & cam sensors), unless you've modified the wiring source to connect from pin B20 - EST 12V Output
    (P1B ECU Connector). This LINK explains why & how to do it. (Holley EFI Wiring Manual, Sections 2.1 "Pin-Outs" & 13.0 "Wiring Appendix")
    Originally Posted by Danny Cabral
    I've never used the ECU's fuel pump trigger wire to directly power the pump (even if it is less than 10 amps).
    I've always used a separate relay (shown below) because that green wire is still only 14 AWG.
    The 2nd fuel pump relay is used so the fuel injectors aren't subjected to the pump's amp draw.
    It's only a 20 amp fuse and it also feeds power to the fuel injectors (& ignition coils - LSx, MOD & HEMI).
    I prefer to use 10 gauge wire due to its long length, especially for high output race pumps.
    Simply use the green fuel pump wire (+12V) to trigger your additional fuel pump relay's coil (+) terminal #86. (Holley 12-753 Fuel Pump Relay Kit)
    (Holley 12-753 Fuel Pump Relay Kit Instructions) (Quick Fuel 30-199QFT Fuel Pump Relay Kit) (Mr. Gasket 40100G Sealed Relay Kit) (Pico Wiring 5593PT Sealed Relay Kit)
    Delphi Metri-Pack 630 Pull-To-Seat female terminals for retrofitting to a sealed relay socket connector:
    #12033997 10/12 AWG (3.0 mm²), #12066614 14/16 AWG (2.0-1.0 mm²), #12020156 18/20 AWG (0.80-0.50 mm²)
    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.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us