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Return style wiring HOW TO allowing OE type fuel pump actuation

Discussion in 'How-To' started by MalcolmV8, Jan 27, 2012.

  1. cj428mach

    cj428mach Well-Known Member Established Member

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    From that link I posted earlier
    "I believe you will have to change the Returnless fuel pump mode scalar value in the tune to 0, and make sure the Return Fuel duty cycle is set to a reasonable value (70% is shown below), to have this work properly."

    In advantage the return fuel duty cycle is a .6999 in AMZ2 did you leave that alone or adjust it any?
     
  2. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Here is exactly what I change in PRP when going from return style to returnless

    Returnless fuel pump --> fuel pump voltage table (set all cells to 15 volts)
    Returnless fuel pump --> scalar --> fuel pump gain integral term = 0
    Returnless fuel pump --> scalar --> fuel pump gain derivative term = 0
    Returnless fuel pump --> scalar --> fuel pump gain proportional term = 0
    Returnless fuel pump --> desired pressure drop across injectors (set to 4 PSI below physical fuel pressure regulator's base pressure)
    System switches --> scalar --> fuel pump type = 0

    That's it.
     
  3. cj428mach

    cj428mach Well-Known Member Established Member

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    Are you not running a FRPS anymore?
     
  4. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Yeah I sure do.
     
  5. cj428mach

    cj428mach Well-Known Member Established Member

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    I thought part of Don's book said if you don't need the FRPS then you set fuel pump type to 0. I was under the impression if you wanted the FRPS to keep doing its thing then you leave it as returnless aka 2.

    I battled the pump priming issue all last night and this morning as I was getting ready for work I think I know where I'm screwing up. I removed the the Brown/pink and Red/black terminals from the FPDM plug and plugged into those terminals on the body harness. I need to be hooking into the brown/pink, and red/black on the FPDM side not the harness side. As I was looking at the stock pump hat the brown/pink wire goes to the hat so by hooking to the body harness I'm hooking to a wire that goes to nothing (I have the brown/wire unhooked at the body plug where the tank plugs in.)

    I hope this fixes it as I'm pulling my hair out trying to get it.
     
    Last edited: May 15, 2014
  6. jblood37

    jblood37 Well-Known Member Established Member

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    The brown/pink wires are wires to fuel pumps right?
     
  7. cj428mach

    cj428mach Well-Known Member Established Member

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    Yep it goes to the stock pump hat.
     
  8. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    That does sound familiar. I'll double check my tune and current notes on it when I'm at my tuning computer. What I gave you yesterday was from my work book notes I made years ago when I started tuning and had it close by for handy reference.

    Again it's hard to follow exactly what you're doing when you say you removed some terminals from a harness etc. Some of the short comings of doing things over the internet :)
    But if you're bypassing your FPDM and taking the wires directly from the ECU that won't work. The ECU sends very low powered signals to the FPDM telling it what to do. Those signals do not carry enough power to energize your relay. You must leave the ECU connected to the FPDM as stock and allow the FPDM to control your relay.

    Again put everything back the way it should be. Let the ECU control the FPDM and leave all the wires there in tack.

    Simply take only these two wires

    Pin 10 = BN/PK (normally fuel pump positive)
    Pin 3 = RD/BK (normally fuel pump negative)

    They normally go from the FPDM to the fuel pumps. Use those to activate your relay.

    Think of those two wires running from the FPDM down to the pumps.... trace them.... half way there cut them and attach to your relay instead of to the fuel pumps. It's really that easy.
     
  9. cj428mach

    cj428mach Well-Known Member Established Member

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    It works now! I was hooking my relay up to brown/pink and red/black on the car harness side instead of hooking them to the fuel pump driver module side of the wiring. Thanks alot Malcolm. I love having my car still act stockish except when you hit the go pedal.
     
  10. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Awesome :beer: Perseverance!
     
  11. kmyers

    kmyers Member Established Member

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    Anymore detailed pictures??
     
  12. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Just added a pinout to first post in thread.
     
  13. Tractionless1

    Tractionless1 Ur Gator Bait!! Established Member

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    Malcolm,

    I sent you a PM today concerning my issues, I didn't even think of posting here. Feel free to copy paste if you'd like the info. here for future reference. Thanks

    Mine's currently wired br/pk on harness side of car to blue of relay's, bk/rd harness side of car to black of relay's and zilch happens with key on. Lethal system whiich previously worked as intended via their instructions, I reattached green/yellow. Both newly tapped wires (above) were completely were cut through and there's a small lenght left at the FPDM plug connected to nothing. If I jumper the green/yellow off of the relay power wire from the battery it fires right up and runs as it should.
     
  14. cj428mach

    cj428mach Well-Known Member Established Member

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    Its been a while since I've done this but you need to be hooking to the FPDM not the wiring harness itself. The FPDM is sending the signal to the pumps so you need your relay trigger wires going to the FPDM not the body wiring harness itself. Thats what I was screwing up on mine.

    If you have small lengths of br/pk and bk/rd hanging out of the FPDM you're hooked to the wrong side. You need to be hooked up to those little wires coming out of the FPDM on the FPDM side.
     
    Last edited: Mar 3, 2015
  15. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Do you still have the harness connected to the FPDM? Some guys pull off the harness and tap the wires there and that won't work. The signals come from the FPDM itself.
     
  16. Tractionless1

    Tractionless1 Ur Gator Bait!! Established Member

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    FOUND IT! Popped the inertia switch, glad it was that easy and probably happened when I connected blues, br/pk, and bk/red together then turned the key. :idea: I'm very surprised the 3 of us working on the car during Monday's dyno session didn't notice, embarrassed even, then again it was an arduous day.
     
  17. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Glad it was easy :beer:
     
  18. crfrider16

    crfrider16 Heretic Established Member

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    Just wanted to say that I've been meaning to do this forever, and finally got my ass in the garage to mess with it. I had it done in 15 minutes. Worked like a charm. Very easy and convenient,since I'm still tuning my car and flashing it over and over.

    Great job Malcolm, thanks!
     
  19. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Very cool :beer:
     
  20. laddanator

    laddanator Active Member Established Member

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    I'm doing a 04 Cobra swap into my 96 Cobra (Everything but the fuel stuff), and wanted to keep my tank, lines, and I have a custom 96 fuel rail (buying one) that fits the 04 intake. I'm just running one 320lph fuel pump, which is plenty for my setup. I was wondering how I would power the FP this way, and then I found this post. I really hope this works for my setup.
     

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