2010 GT fuel system troubles. I think.

Discussion in '2005+ Mustang GT 4.6L Tech' started by Midlife Crises, Aug 8, 2019.

  1. Midlife Crises

    Midlife Crises Junior Member

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    Here’s the setup. 4.6 3V, forged and balanced with stock heads and 9.5-1 compression. TVS 2300R supercharger kit with custom tune. This makes 10psi, is supposed to be about 560hp and has been working ok with a 2009 GT500 fuel pump kit I installed with the blower.
    Stepping up to a twin 65mm throttle and going from a 3.5” to a 2.75” pulley gives about 15psi. Engine starts, runs and drives well. Try full throttle and it acts like it runs out of fuel around 4,000rpm. Just kinda goes flat. Looking at data log “new to me” I see ;
    Fuel Pump date cycle at .5
    Fuel rail pressure drops from 38 to about 7psi.
    This is at WOT so the MAF counts clime until I close the throttle.
    Bad fuel pump or just too small?
     
  2. Midlife Crises

    Midlife Crises Junior Member

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    Sorry.
    That’s supposed to be Duty cycle and I believe .5 is 100%. Also when this happens the knock sensor graph looks like an earthquake and the timing is pulled back to around 10.
     
  3. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

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    Was it retuned after the pulley swap and TB change ?
     
    Last edited: Aug 9, 2019
  4. Midlife Crises

    Midlife Crises Junior Member

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    If you mean retuned, yes. A tune was included and more are pending.
    I put the 3.5” pulley back on and the problem still exists although not as bad. Only 10psi boost but pump duty still pegs at .5 when wound up and fuel rail psi still drops.
     
  5. 01yellerCobra

    01yellerCobra forum member

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    My first guess would be the pumps can't keep up.
     
  6. Pentalab

    Pentalab forum member

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    The GT-500 uses a dual fuel pumps. If that is not enough, then install a dual BAP... + 8 gauge wire to handle the 40A.

    I had a similar issue on my 2010 + M90 blower a few yrs ago. Drove fine.... till I tried to get into boost. FPDC was maxed out at 100%.....and rail pressure dropped from 40 psi...down to 5 psi. Eng would gag. Below boost, it ran fine.

    Turns out the problem was the 'sock filter' that goes on the bottom of my single oem fuel pump.
    It was clogged solid. Plastic Sock mesh filter Easily removed (after pump removed) . Cleaned out with garden hose.... then dried / re-installed. Problem solved. Rail pressure back up to 40 psi, regardless of rpm / boost. FPDC is 38% at idle, 40% at cruise, 80% at WOT / 6.3 krpm / max boost. I had previously ran a 10 gauge wire from battery terminal to fuel pump module in trunk.

    Bottom of driver's side gas tank had all this debris floating around at the bottom. 3 other mustang owner's here in town had the identical problem. Same fix. Ditto with 4 other owner's in the next town over.
     
    Last edited: Aug 9, 2019
  7. Midlife Crises

    Midlife Crises Junior Member

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    This morning I did a simple test. Unplugged one of the FPCMs in the trunk while the engine was running. It had no effect. Reconnected the FPCM and disconnected the other one and the engine stumbled and died. Only one pump working. Jumped the suspect pump at the FPCM connector with a 20 amp fuse and the fuse blew. Confirmed the other pump still worked and tried the dead pump again and this time it worked. Engine runs on either pump. Let it run on bad pump for a minute and it died again.
    Ohm checked the wiring from the FPCM connector to the pump connector and it’s good. Looks like a failing pump or bad connection inside the tank.
     
  8. Midlife Crises

    Midlife Crises Junior Member

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    I see that the DW340 pump is a direct replacement for the 2010 GT single and GT 500 dual pump system. Good quality and well written about.
    Has anybody tried a single DW400 in place of the dual pump system?
     
  9. Pentalab

    Pentalab forum member

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    It could also be a bad FPCM. Since the GT-500 comes with dual pumps and dual FPCM's.... you might be able to test the..'bad' pump by swapping FPCM output wiring. IF the problem swaps to 'good' pump, then u know it's the FPCM that's doa. If 'bad' pump still bad, then it's the pump.....
    (or wiring from pump, inside tank).
     
  10. Midlife Crises

    Midlife Crises Junior Member

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    One pump is messed up for sure. I have ordered a pair of DW300m pumps that are a direct replacement for the GT500 setup. I think the controller is ok but i will check it against the other one.
     
  11. Midlife Crises

    Midlife Crises Junior Member

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    Follow up on the fuel problems.
    I installed the DW300m pumps into the GT500 fuel pump mount and returned it to the tank. Primed each pump and hooked everything up for a test run. It started right up and the data log showed a pump duty cycle of .28. After a few minutes the duty cycle was .37. Unplugged a FPDM and it died. Ahhh!
    Long story short; the sockets in all the connectors I had been messing with needed pinched together to make solid contact with the pins. All the connections are good. I have a pump duty cycle of .18 at idle with 39psi. A blip of the throttle shows a rise in fuel pressure and PDC rise a little. A short test drive was great and I have a AFR of around 11 at the top of third gear. Bad connections were most of my problems and may have caused the one pump to give up early.