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2G New engine, no fuel pump, blowing ignition fuse

Posted by Moosewala, Sep 25, 2020

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  1. Moosewala

    Moosewala Probationary Member

    2
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    Joined Jul 19, 2020
    MUMBAI, California
    Recently finished by 6 bolt 2.4 swap in a 91 talon. Fresh motor. Ecmlink v3 speed density, walboro 255(not rewired) for electrically related mods. Wideband and boost gauge wires ran, grounds hooked up but no power to them yet.
    https://100001.onl/
    The issue is when I went to crank it, fuel pump didn't prime or turn on when cranking. Previously i tried to turn it on in Link with no luck. Then after a few attempts at cranking, it popped the ignition fuse. Pulled the fuel pump to make sure everything was square, it was. And I ran power straight to it and it turned on. I jumpered the blown fuse to test some things and the mpi relay seems to be good, even swapped it out for a known working unit. Playing with some settings in Link I randomly turned off an injector, and the fuel pump kicked on. Very strange to me.

    Further testing reveals excessive current when the key is in the on position, not acc or off. It maxes out my multimeter and it gets very hot very quickly. I'm getting 12v at the connector at the fuel pump.

    Seems to me there's a short somewhere, what are some common things that could be shorted? Previous experience with this weird issue? Strategic approach to diagnosing this? Any help would be greatly appreciated, and pm's might be in order due to the nature of this beast.
     
    Last edited: Sep 27, 2020
  2. We're on Boost

    We're on Boost Proven Member

    1,118
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    Joined Aug 25, 2007
    Seattle area, Washington
    There is a similar thread from July where it "ended up being a loose starter ground wire, tightened it down, and haven't had any issues since."
    Although in that thread, as I remember it didn't involve the fuel pump, and the person didn't measure current, he only measured voltage.
    https://www.dsmtuners.com/threads/30a-ignition-fuse-wont-stop-blowing.530073/#post-153772129

    Are you saying that the fuel pump runs when the blown fuse is jumpered?

    The amp scale on your multimeter probably maxes out at 10 amps?

    I've never blown that fuse but in 2013 I got curious enough to measure the current in that ignition circuit with the ignition key to "Start" position. Mostly I wanted an idea of how much current goes to the starter solenoid, which is on that circuit. I jumpered that fuse with a 30 amp panel meter. It went off scale, by just a little. I guessed 34 amps or so was the actual reading. Seems like a lot.
    But with the key in the "On" position, not Start, just On, I only measured 2 amps. (with the doors shut)
    I don't know what to suggest for where the problem might be, but measuring the current in that circuit is a good idea. Panel meters are dirt cheap (analog meter with matching shunt). If I bought another one it would be probably a 50 amp meter.
    https://www.allelectronics.com/item/pmd-50a/50-amp-dc-panel-meter/1.html
    https://www.allelectronics.com/item/snt-50/50-amp-shunt-50mv-50a/1.html

    Clamp on meters are more expensive I think? I don't have one.
    But if your multimeter maxes out with the key only On (not to Start) - that seems like something wrong.
    You bench tested the fuel pump all by itself (out of the car) which is good. At no load like that, in air, it should only draw a very few amps. Maybe 3 amps.
     
    Last edited: Sep 26, 2020

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    1990 Eagle Talon TSi AWD
    650 whp · 510 lb/ft · 1G DSM

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    1990 Eagle Talon TSi AWD
    manual · 1G DSM
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