Results 1 to 4 of 4

Thread: Fuel pump #1 over runs sometimes.

  1. #1

    Default Fuel pump #1 over runs sometimes.

    After the engine has been running a bit the fuel pump continues to run when shut off. A second key on-off always stops the pump. The pump is the Holley 12-1200. It draws 9 amps per motor and is powered by the green wire from the harness relay. Stage 2 activates @ 3,300 RPM via MSD window switch. I've also experienced the fuel pump run when I turn on the battery switch on with key off. ECU power is dedicated marine style posts on battery not affected by battery switch. Is this a defective unit? I went to a dyno shop recommended by Holley Tech and he said add a separate relay. My understanding is a separate relay is for higher amp loading. Also the switched +12V is connected to the post on the Ford starter relay.

  2. #2
    Join Date
    Dec 2009


    Quote Originally Posted by dynosore View Post
    After the engine has been running a bit the fuel pump continues to run when shut off. ...and is powered by the green wire from the harness relay. (System Relay & Injector Wiring Troubleshooting)
    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.

  3. #3


    Thanks Danny. I've read that one before, my mind is just a little weary. I'll disconnect the battery. But you got me thinking. I started having this same problem last year! Could there be something fishy with the switched +12V on the solenoid post? I'll let the Electrical Engineers explain it, but I bet an alternate switched +12V source solves this issue.

  4. #4


    It's bizarre! After a fluttery test run after putting the 60 lb/hr injectors back in, and connecting to the same +12V circuit that switches the MSD 6AL, I had to key off the ignition twice to stop the fuel pump. I went in the house a few minutes and when I came back to the car the Fuel Pump was running again, KEY OFF! I left the Battery disconnected over night and the "Tuning Pro" flashed my ECU from build 130 to 160, and I've switched to my new laptop that has never been connected to the ECU. It's not the ignition switch, nothing else powers up. The MAP sensor is rock solid @ 1800-2000 RPM when it flutters, the AFR indicates misfire. Ignition misfire or lean misfire? It seems happier at 12.8 Target AFR than 13.5, but that's to fat and it still runs rough. Anybody know the SWAG method?

    UPDATE: It's Fuel Pump #2 that's been over running. It's controlled by an MSD window switch and is non-ECU related. Sorry for wasted mental energy. The SWAG method was described to me by Lineman setting up 3 Phase transformers. They spoke of Ys, Open & Closed Deltas, High Legs & Wild Legs. "But sometimes the electricity doesn't do what it's supposed to." Then the SWAG Method is employed if the WAG Method fails. Scientific Wild Arss Guess.

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