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Pumps won't cycle off???

Discussion in 'Engine/Tuning' started by turbov6joe, Nov 2, 2015.

  1. turbov6joe

    turbov6joe Defensor Fortis Established Member

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    I'm having issues with the fuel system providing too much pressure to the rail at idle (60-62 psi). Today I figured out that the pumps are continuing to run after the key is turned on....they are not cycling off. There is 13.3v at the pumps at idle. I've done a search and have read several things, once of which saying it was a ground issue. Can anyone shed some insight as to what the issue(s) may be? I'm losing my mind from staring at the wiring in the trunk and am ready to take a match to my baby....HELP :(
     
  2. GodStang

    GodStang Well-Known Member Established Member

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    Any info on fuel system you are running?
     
  3. Rich'sTRsvt

    Rich'sTRsvt Member Established Member

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    I believe on the stock returnless system the ground is what cycles on and off so if the ground wire was pinched it could cause the pumps to run constantly with the power on.
     
    Last edited: Nov 2, 2015
  4. turbov6joe

    turbov6joe Defensor Fortis Established Member

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    Of course:

    twin GT supercar pumps
    Fore Hat
    80's
    KB BAP
    Dual FPDM's
    Hotwired from battery to a relay, then out to the loop.
    I'm using a premade dual FPDM harness

    The wires going to the pumps are seeing 13.3v. The FP duty cycle on the Xcall 3 is saying .05???
    I've swapped out 4 FPDM's, 3 FRPS, and a new FRPS I bought today just to be sure. The idle FP is 60-62 psi with the line on, and ~50-52 psi with the line off (the line draws 20" of vacuum). When I unplug the FRPS the rail jumped up to 77 psi. I took the BAP off line and that didn't change anything. I'm hearing that there is likely a ground issue causing the pumps to run full boogie at idle....they drop to 11v with key on, motor off. What else could control the fuel pressure? I even dropped the stock tune back in just to be certain...nothing. There has got to be so wire issue, I just can't seem to find it. SO....I pumped out a full tank of e85 today and am going to drop the tank to look things over. I fee like it's something dumb because t hasn't always been an issue...it started about 2 months ago off and on.
     
  5. turbov6joe

    turbov6joe Defensor Fortis Established Member

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    Which ground wire you referring to?
     
  6. Rich'sTRsvt

    Rich'sTRsvt Member Established Member

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    The ground wire coming off of the pumps. I remember someone else having a similar issue after installing fore hat and gt pumps.
     
  7. turbov6joe

    turbov6joe Defensor Fortis Established Member

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    Found the problem(s)...both ground wires for the fuel pumps had been rubbing on the body and grounding out. The insulation on the solder connections rubbed off. I was lucky to find it, I would have never seen if I didn't pull the hat out and flip it over....the shop lights were shining on it just right. All is good now after I ripped out what hair I had left.
     

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