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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. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Switching from returnless to return here's what I do in PRP.

    Returnless fuel pump --> Fuel pump voltage table - set all cells to max, usually 15
    Returnless fuel pump - scalar
    - fuel pump gain integral term - 0
    - fuel pump gain derivative term 0
    - fuel pump gain proportional term 0
    Returnless fuel pump - desired pressure drop across injectors - (set to 4 PSI below base pressure set of fuel pressure regulator).
    System switches --> scalar --> fuel pump type - 0

    Hope that helps.
     
    Last edited: Nov 12, 2015
  2. lcaptmorg

    lcaptmorg New Member Established Member

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    Awesome thanks. I noticed that in earlier post but just wanted to make sure info hadn't changed..

    Did you end up running a grounding swtich to be able to turn the pumps on to set base fuel pressure. IF so which one did you use. I figured I could run an extra lead off the relay though a switch to a chasis ground. I heard you mention the yellow wire lead as well.
     
  3. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Yes I have a small toggle switch mounted up by where the Amps are out of the way. It grounds pin 3 of the FPDM to chassis ground turning on one of my pumps continuously. Then with engine off but the pump running I adjust base pressure on the fuel pressure regulator.
     
  4. lcaptmorg

    lcaptmorg New Member Established Member

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    Im my prp if I change the fuel pump type from 3 to 2 then the function for "returnless fuel pump" goes away . Therefore no way to change desired pressure drop across injector. Nothing in Lasotas book about changing the fuel pump type. Thinking I will leave it 3.
     
  5. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    It's on page 42 of Lasota's book. You actually change it to 0 not 2. Sorry about that, I just went back and looked in the tune itself. The post above was from some notes I had taken obviously with an error. I edited my post above.
    It may also vary for different strategies. I'm using AMZ2, read the help that comes down below in PRP.
    0 = non-returnless
    1 = mechanical returnless
    2 = electronic returnless

    Those are all the options I have. I'm unable to set that to a 3. 2 is max value. What strategy are you using?
     
  6. lcaptmorg

    lcaptmorg New Member Established Member

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    MSE3 strategy.

    Setting of 0 if the FRPS has been deleted.

    I kept the frps in so wouldn't use that setting. Weird. I know there are some diffrences in strategies. I will check my mach 1 zya2 to see if its different.

    Started it up today and so far has ran and drove quite nice. I have yet to do any wot pulls though.
     
  7. lcaptmorg

    lcaptmorg New Member Established Member

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    ahhh I see it now . 0,1,2,3 is under fuel pump type. 0,1,2 is under fuel pump system type.

    With the FPRS on the rail I left 3 and 2 respectively.
     
  8. MalcolmV8

    MalcolmV8 Well-Known Member Established Member

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    Cool glad you got it. I saw in Lasota's book there's both "fuel pump system type" and "fuel pump type". My AMZ2 only has "fuel pump type".
    I also keep the FRPS. It's a good idea as the ECU will use it to increase or decrease injector pulse width to compensate for minor fluctuations in fuel pressure to keep drivability at its best.
     
  9. laddanator

    laddanator Active Member Established Member

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    Weirdest thing. When I did my 04 Cobra swap into my 96 Cobra last year, I wired the relay as described on the first post. Pump primed key on, then shut off. I'm using the stock 96 fuel lines, as this car is return style. I drove the car this way for 4 months, no issues fuel wise. I decided to build a brand new motor, using a Cobra Engineering M122 kit, so I was not able to use my modified stock 96 Cobra fuel rails as I had before on the 04 setup. I ended up using my 04 Cobra rails with NO FRPS. I'm using a Division X fitting where the FRPS went, to feed a bypass regulator after the rails. I changed NO wiring to the relay, and using the same computer that was tuned for the swap last year. The car will start up, and run fine, but when I come to a stop, the car will shut off. This was driving myself, and my tuner crazy! Just for kicks, we wired pin 3 to chassis ground, and as expected, pump runs all the time with key on. Here is the kicker, this also solved the problem of the car shutting off at a stop.

    I'm not understanding why the car ran for the months, no stall issue, but now it stalls, and no wiring has changed? The only thing that has changed from the last build to this build, is the 04 Cobra rails, and bypass regulator.

    I'm not exactly sure my tuner setup the return tune as you have here

    Returnless fuel pump --> Fuel pump voltage table - set all cells to max, usually 15
    Returnless fuel pump - scalar
    - fuel pump gain integral term - 0
    - fuel pump gain derivative term 0
    - fuel pump gain proportional term 0
    Returnless fuel pump - desired pressure drop across injectors - (set to 4 PSI below base pressure set of fuel pressure regulator).
    System switches --> scalar --> fuel pump type - 0

    But regardless, the setup worked fine for months last year.
     
    Last edited: Jul 11, 2016
  10. VinnyGT

    VinnyGT Member Established Member

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    Does anyone who has done this mod have a picture. I'm not sure if you only connect your relay positive and ground to the wire coming from the ecu and leave the half of the wire for pin 10 and 3 on the connector for the fpdm hanging. Or do you simply splice the relay power and ground wires into the wire 10 and 3 leaving it connected to the fpdm like stock?

    Thanks for the answer/picture in advance.
     
  11. MG0h3

    MG0h3 Premium Member Premium Member Established Member Established Member

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    Just got done doing this and I used a couple 40amp relays rather than the FORE one.

    Couple notes if you go this route and are using a HOBBS to fire the second pump: Since youll be using pin 10 (originally fuel pump power) to power the relay, open up the harness about 6" downstream from the FPDM and youll find a nice factory junction where it splits into two wires to feed both pumps. This is handy as an easy way to have both relays powered from KEY ON power.

    I went this route because I wanted to have the HOBBS controlling a ground, mainly for ease but also to limit extra hot wires running back to the truck.

    A quick and easy way to have the pump run full time for whatever reason (leak checks or fuel pressure adj.) is to unplug the hobbs and insert a mini fuse in the plug.
     
  12. Natedogg1701

    Natedogg1701 New Member

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    Sorry for resurrecting an old thread here, but hoping to get a few answers.

    Did you ever diagnose as to why you were losing time? It just makes no sense unless the wiring was causing FRPS issues and it was changing things in the tune while driving.

    So you brought Pin 10 to REMOTE and ground where? The main ground terminal that the 4 gauge ground goes to also? And did this work fine for you?



    Thank you all in advance.
     

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