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Thread: FPCM is making my life miserable.

  1. #1
    Senior Tuner IDRIVEAG8GT's Avatar
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    FPCM is making my life miserable.

    Hey guys, here's another thread that concerns weird things that a GMT900 series pickup does. After the addition of my new fuel system I have been battling my FPCM, and the boost referenced regulator.

    I'm running a twin Walbro 255 in tank fuel pump setup, one fuel pump being powered off the trucks fuel pump circuit, the other connected to a Kenne Bell BAP, which is triggered off of a Hobbs switch set to 3 psi boost.

    Problem is, the regulator is set to 58psi then boost referenced off the manifold.

    The FPCM however only knows low flow, normal, and high flow conditions. So I set normal and low flow to 53psi as that's where it idles at with vacuum on the manifold, and 72psi for high flow as that's 14psi boost.

    Problem is, at mid boost levels the FPCM is commanding 72psi fuel pressure but delivered fuel pressure due to the regulator is only 66psi or so as it will only be boosting 8 psi which trips a CEL of the fuel rail pressure sensor going haywire.

    How in the hell do you get around this problem? Is there a way to just disable the FPCM and let the primary pump run at 12 volts all the time without the CEL being tripped? I can't disable it in the tune
    Last edited by IDRIVEAG8GT; 04-09-2012 at 02:38 AM.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  2. #2
    Senior Tuner DSteck's Avatar
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    Unplug the FPCM, fix the codes, and power the pumps straight off the battery with a relay for ignition on power only.

    DSX Tuning - St. Louis, MO
    Injector Dynamics dealer/supporter/lemming
    Need a plug-and-play 2.5 or 3 bar LS1/2/6/7 MAP sensor? PM me
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  3. #3
    Senior Tuner IDRIVEAG8GT's Avatar
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    Quote Originally Posted by DSteck View Post
    Unplug the FPCM, fix the codes, and power the pumps straight off the battery with a relay for ignition on power only.
    Even if I disable the FPCM, there's no way to turn off/get rid of the codes.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  4. #4
    Senior Tuner DSteck's Avatar
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    If you unplug it completely, sure there is. The module itself can't throw a code, and you'll just have loss of communication, which you can turn off.

    DSX Tuning - St. Louis, MO
    Injector Dynamics dealer/supporter/lemming
    Need a plug-and-play 2.5 or 3 bar LS1/2/6/7 MAP sensor? PM me
    http://www.facebook.com/dsx.tuning

  5. #5
    Senior Tuner IDRIVEAG8GT's Avatar
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    Hmm, I wonder if I can simply pull the FPCM fuse..... Then run the existing wires that power the fuel pump off the FPCM to the terminal stub on the fuse box.

    Then that would leave the eliminate the need for the actual rail pressure sensor and all that other crap.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  6. #6
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    Quote Originally Posted by IDRIVEAG8GT View Post
    Hmm, I wonder if I can simply pull the FPCM fuse..... Then run the existing wires that power the fuel pump off the FPCM to the terminal stub on the fuse box.

    Then that would leave the eliminate the need for the actual rail pressure sensor and all that other crap.
    how did it go?
    NotoriouSS TAD
    J5 - 96' Impala SS - autocross / drag / multi purpose driver / 4L60E assasin
    Rosie - 67' El Co - autocross / drag / wifes multi purpose driver
    SAVE SO-CAL DRAG RACING!!

  7. #7
    Senior Tuner IDRIVEAG8GT's Avatar
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    Quote Originally Posted by ProTools4 View Post
    how did it go?
    I'm actually still working on it now.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  8. #8
    Advanced Tuner vette_c6's Avatar
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    keep us update after you finish ,,

    specialize in: V8 Tuning (Kuwait)
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  9. #9
    Senior Tuner IDRIVEAG8GT's Avatar
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    Quote Originally Posted by vette_c6 View Post
    keep us update after you finish ,,
    Well, I'm just trying to figure how to power the relay and keep everything under the hood civil. Motor is totally out right now as we lifted a head and blew a gasket at 22psi. :O

    So needless to say, there is a mess of wires strung everywhere to sort through lol.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  10. #10
    Pins 85 and 86 power the relay.
    Jake

  11. #11
    Senior Tuner IDRIVEAG8GT's Avatar
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    Quote Originally Posted by smokeshow View Post
    Pins 85 and 86 power the relay.
    The actual fuel pump?
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  12. #12
    I was being sarcastic haha. But yeah pretty much all relays use the same pins for the coil trigger.
    Jake

  13. #13
    Senior Tuner IDRIVEAG8GT's Avatar
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    G'damn! that's useful to know.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  14. #14
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    here is my controbution

    it is yet to go on the dyno
    But it works on the rack
    hope this helps someone



    test car
    2010 Silverado 2-wheel drive 5.3
    LSX376 w/ cogged 2300 Maggy
    walbro 400 pump
    AN send return fuel lines w/ rising rate adj return reg

    process to delete FPCM with return fuel system
    Unpluged the FPCM
    *under the bed of the trucks above the spare
    *passenger side rear seat under the quarter window on the 5thgen camaro
    Large Pins 47 & 16 with around 10 gauge wire supply ground and power to the pump
    ground is Pink ...WTF~!
    Depin the connector and repin for new weather pack relay
    Pin 13 Dark Green / white stripe is the trigger form the PCM key hot.

    in HPT turn off P0230 and U0109

    go make power!
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    Last edited by ProTools4; 05-04-2012 at 01:39 PM.
    NotoriouSS TAD
    J5 - 96' Impala SS - autocross / drag / multi purpose driver / 4L60E assasin
    Rosie - 67' El Co - autocross / drag / wifes multi purpose driver
    SAVE SO-CAL DRAG RACING!!

  15. #15
    Senior Tuner IDRIVEAG8GT's Avatar
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    Quote Originally Posted by ProTools4 View Post
    here is my controbution

    it is yet to go on the dyno
    But it works on the rack
    hope this helps someone



    test car
    2010 Silverado 2-wheel drive 5.3
    LSX376 w/ cogged 2300 Maggy
    walbro 400 pump
    AN send return fuel lines w/ rising rate adj return reg

    process to delete FPCM with return fuel system
    Unpluged the FPCM
    *under the bed of the trucks above the spare
    *passenger side rear seat under the quarter window on the 5thgen camaro
    Large Pins 47 & 16 with around 10 gauge wire supply ground and power to the pump
    ground is Pink ...WTF~!
    Depin the connector and repin for new weather pack relay
    Pin 13 Dark Green / white stripe is the trigger form the PCM key hot.

    in HPT turn off P0230 and U0109

    go make power!
    :nohomohug:

    But it's under the spare?! thats where that goofy bunch of wires went lol.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  16. #16
    Senior Tuner IDRIVEAG8GT's Avatar
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    And also, could you simply not cut the hot wire trigger for th FPCM then wire it to the power for the fuel pump. Wouldn't that eliminate the need for the relay? And then the FPCM fuse would simply act as the fuse for the fuel pump? Or am I thinking wrong here.
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  17. #17
    Isn't your truck a 2007? Pretty sure 2007s in certain applications didn't have an FPCM, so it has to have the manual relay trigger. Pin 50 on the X1 ECM connector, DK GRN/WHT wire. That is what I am currently using until I can get my FPCM operational. Mines an 08 and still has the trigger, so you should be fine.
    Jake

  18. #18
    Senior Tuner IDRIVEAG8GT's Avatar
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    Quote Originally Posted by smokeshow View Post
    Isn't your truck a 2007? Pretty sure 2007s in certain applications didn't have an FPCM, so it has to have the manual relay trigger. Pin 50 on the X1 ECM connector, DK GRN/WHT wire. That is what I am currently using until I can get my FPCM operational. Mines an 08 and still has the trigger, so you should be fine.
    Nah mine is an 07 but it does have the FPCM voltage modulator
    08 Panther Black G8 GT, VMR V713's Powder Coated Gray,

    Blown, Heads, Cam, Lightened, Forged, Stalled, and is just my DD.

  19. #19
    Tuner in Training
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    If I remember correctly if you unplug the FPCM you have to jumper the GMLAN wires to keep the communications bus in tact. May cause other system issues if you leave the FPCM disconnected.

    When you are done with the mods, disconnect the battery and measure pins 6 & 14 on the aldl. If they are 120 ohms and not 60 ohms you need to fix your can bus. (FPCM has passthrough communications)

    John

  20. #20
    I'm running a dual pump setup on an 08. I'm using the racetronix harness and relays to power the pumps. Also bought a transistor from ADM performance to use low voltage power from the ECM to trigger a low voltage relay which triggers the racetronix relay. Remove the fuse for the FPCM and tune on the communication codes. Works great. I've got a wiring diagram around here some where of how I wired everything. ADM has used the transistor in the past to defeat the FPCM on the 2010+ camaros.