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Thread: Short to ground on fuel pump output.

  1. #1

    Default Short to ground on fuel pump output.

    Fuel pump fried internally somehow and blew the fuel pump fuse. After replacing the fuse I found that it was no longer operational. Everything else seems to work fine, minus the fuel pump output signal. Has this happened to anyone else and I know there are no internal repairs on these units. My next move will be a toggle switch wired straight to the battery. Any other advice?

  2. #2
    Join Date
    Dec 2009
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    Connecticut
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    Try completely disconnecting the battery for 20 minutes. This "resets" some unusual ECU issues.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, Moroso vacuum pump, cold air induction, dual 3" exhaust/Magnaflow mufflers, 100HP progressive dry direct-port NOS, A/C, Lentech Strip Terminator wide-ratio AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, custom traction bars, 4" lift, 35" mud tires

  3. #3

    Default

    Tried that already with no luck. I unhooked it with the thought of sending it in for repairs then found out it wasn't possible. The pump truly shorted out internally, but the fuse didn't save it. Do the inputs & outputs fry internally if hooked up wrong or encounter a short? I would hope an internal mechanism exist to protect the board.
    Last edited by clockwork826; 05-12-2017 at 02:23 PM.

  4. #4
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    Dec 2009
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    Connecticut
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    I'm told there is some protection built in, but like an OEM ECU, there are certain things that it can't survive. As a last resort, you can try reflashing the ECU firmware. In a few cases, this has rectified certain inoperable ECU functions.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, Moroso vacuum pump, cold air induction, dual 3" exhaust/Magnaflow mufflers, 100HP progressive dry direct-port NOS, A/C, Lentech Strip Terminator wide-ratio AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, custom traction bars, 4" lift, 35" mud tires

  5. #5

    Default

    Output of ECU to fuel pump "relay" is a small, generally 2 amps of current transistor. Generally, it has a diode on it's output that would burn out.

  6. #6
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    Aug 2012
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    Dayton, OH
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    Is there any chance the relay itself was also damaged? That might be a place to start. Otherwise, an option may be to use a custom Output to provide a +12V trigger wire to a relay, that runs your new fuel pump. I'm not sure what pump you were using, but most need to be run from a relay.
    93 Notchback, 383ci SBF, Highports, 80mm turbo, custom cam, TH400

  7. #7
    Join Date
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    Connecticut
    Posts
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    Default

    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, Moroso vacuum pump, cold air induction, dual 3" exhaust/Magnaflow mufflers, 100HP progressive dry direct-port NOS, A/C, Lentech Strip Terminator wide-ratio AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, custom traction bars, 4" lift, 35" mud tires

  8. #8

    Default

    Also, check & see if your relay has a built-in internal protection diode. These could short, and on some oddball relays the diode is actually reversed polarity.

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