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Accidently hooked main harness battery leads up backward

Discussion in 'FAST Support Forum' started by portmod7, Mar 8, 2019.

  1. portmod7

    portmod7 New Member

    Dec 7, 2015
    Hello everybody,

    I just installed an XFI ecu and harness on a motor. This is in a race car that already had the exact same setup in it, but the new engine came with a new ecu and proper tune, and the old harness was looking pretty sad so it got replaced.

    I got all done with the install, the last thing I did was hook up the main power leads of the harness to the battery, only I attempted to attach them to the battery backward by mistake. I had the positive lead hooked securely to the negative post of the battery, and as soon as I touched the negative lead to the positive post I got sparks that instantly told me something was wrong and I realized my mistake. The main power leads for the MSD Digital 6AL were also in the mix, but they have their own ring terminals.

    So, I checked the fuses on the harness and they were OK. I thought I must have gotten lucky and not hurt anything. I flipped the switch, hit the start button and the engine fired to life. It wasnt running perfect, but I was told the tune isn't perfected yet and the car is headed to a chassis dyno. So the rest of the day I fired it off several times to circulate water and other fluids and such. It would run, but the idle was set too low to run without babysitting it. At the end of the day I went to fire it up and drive it on a trailer, and couldnt get it to stay running more than a few seconds. It was acting as if I was shutting the ignition off or something, just a nice clean shutoff, no stumbling or anything.

    Now that I've written a novel, my concern is that by hooking the power leads up backward and getting some sparks, I fried something inside the ecu that's giving me problems. Is that a possibility? The fact that it will run and all my sensor readings look normal tell me no, but I am far from an electronics expert.

    I can't attempt to get a log or run it until next week at this point. But I'll be losing sleep over it all weekend.

    Any input is appreciated!
  2. Fastmanefi

    Fastmanefi Well-Known Member

    Jun 4, 2011
    Sonora, CA
    You are probably okay, since you had said that the tune probably wasn't the best anyway. I could do a remote login and check everything out and then finish the tune for you if you want.

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