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Thread: It fires without the fuel pump on.... Dies when you kick the pump on.

  1. #1
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    Default It fires without the fuel pump on.... Dies when you kick the pump on.

    We solved on issue and of course I now have another. I got the engine to fire up last night about 2am. If I turned the ignition on and the fuel pump on for about 3 seconds and then off, the car would fire up and run like everything was normal. It idled and revved no problem. However, as soon I turn the fuel pump on the car would flood out and die. I know that it has something to do with the big injectors but just not sure what. We tried several different ways adjusting the injector timing, trim, pulse, etc.. nothing worked. I have 160lb injectors and I run resistors since they are low impedence. Don't tell me it won't work because this set up runs fine on my pcm that is tuned using Hptuners. It revs fine and idles fine.

    Any ideas? I am going to post on LS1tech also.
    1969 Chevelle
    Stock 5.3, twin PTE62/62's
    E85, No intercooler
    Th400, PTC Convertor, 3.90 Gears
    Meth/Water Injection
    Factory PCM, Wiring Harness
    EFILive,V1, Daily Driver

  2. #2
    Joe (Moderator) joecar's Avatar
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    Hi Sinister,

    is your FPR located at the fuel rails (MAP-referenced) or at the tank (non-referenced)...?

    what is rail pressure with engine running (with reference hose removed from FPR if applicable)...?

    for those injectors (160 lb/hr @ 3 bar), was IFR table calculated for your measured rail pressure (in your EFILive tune file)...?

  3. #3
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    My FPR is located at the rails. I have a -10 fuel lines from the tank to a "Y" fitting. A single -10 off the Y to another Y fitting before the fuel rails. I then have the FPR at the front of the engine off the fuel rails. It is set at 50psi and stays there when running. When the car was running on HP tuners it would jump up to 65psi when the second pump would kick on at 4psi via a hobbs switch. I have never checked it with the hose off but I believe when it was tuned on the dyno they mentioned it would drop 5lbs of pressure if you removed the reference.

    The IRR table was calculated for 50psi for 160lb injectors and a 2 bar, not 3 bar. My GM Map and the HPtune was 2 bar. I believe this tune on EFI live is also 2 bar.
    Last edited by Sinister; May 2nd, 2012 at 02:10 PM.
    1969 Chevelle
    Stock 5.3, twin PTE62/62's
    E85, No intercooler
    Th400, PTC Convertor, 3.90 Gears
    Meth/Water Injection
    Factory PCM, Wiring Harness
    EFILive,V1, Daily Driver

  4. #4
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    Here is a shot of my fuel regulator location.



    Here is a picture of my control panel. Ignition switch, Push button start, Toggle switch (Fuel pump) Toggle switch (fans) LM1

    1969 Chevelle
    Stock 5.3, twin PTE62/62's
    E85, No intercooler
    Th400, PTC Convertor, 3.90 Gears
    Meth/Water Injection
    Factory PCM, Wiring Harness
    EFILive,V1, Daily Driver

  5. #5
    Joe (Moderator) joecar's Avatar
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    I see the reference hose is removed from your FPR (do I see it right...?)... so the rail pressure should stay steady at what you set it at 50 psi;

    If the manifold reference hose is on, then the FPR regulated rail pressure should go up/down as manifold pressure (MAP) goes up/down.

    I don't follow by the FPR would allow pressure to jump to 65 psi with the second pump running... shouldn't the FPR regulate the pressure to 50 psi...? (unless the return line was too small or otherwise obstructed) (when the pressure jumps to 65 psi, then the IFR would be incorrect, this would need the VE table to be different).


    Ok, understood, 160 lb/hr @ 43.5 psi rescaled to 50 psi, this is what IFR was calculated for ( i.e. at 50 psi they flow 172 lb/hr )[ at 65 psi they flow 196 lb/hr ].



    [ or, is the IFR in your EFILive tune file the same as the IFR in your HPTuners tune file...? ]

  6. #6
    Lifetime Member minytrker's Avatar
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    It honestly just sounds like you need it tuned. You just cant copy a 2 bar HPT tune over to a 2 bar EFI live tune.

  7. #7
    Joe (Moderator) joecar's Avatar
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    Very good point... EFILive and HPT use un-used memory in different manners to implement their COS's.

  8. #8
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    The picture is when we were building everything. Ie, not complete. I do have the reference hose hooked up. The fuel pressure is steady while trying to start it. It seems to initially jump up when the second pump kicks on but that was when it was running at WOT. As far as copying a tune. This is not the first tune. I have had it tuned and it did not start or run at all. So.......I copied the HPtune into a new EFI live tune and I can get it to run without the fuel pump on. The previous tunes is from those who have done several tunes and had no issues. Something must be going on with the injectors and the resistor numbers to make it run.
    1969 Chevelle
    Stock 5.3, twin PTE62/62's
    E85, No intercooler
    Th400, PTC Convertor, 3.90 Gears
    Meth/Water Injection
    Factory PCM, Wiring Harness
    EFILive,V1, Daily Driver

  9. #9
    Joe (Moderator) joecar's Avatar
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    Hmmm... I see, the key point here is that it runs with the fuel pump off and not with it on...

    can you draw a diagram showing how the resistors are connected between the injectors and the harness.

  10. #10
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    I tried to take some pictures from under my dash. Not the best but I think you can see how we did it. We wired in a inline resistor to the power side. Basically cut the wire before the injector wire goes into the pcm and then wired the resistor between the two wires. We put one resistor for each injector. We also staggered the resistors so they would never touch each other or be against any other metal or wires due to them getting hot.

    I am not sure if this would make a difference but since I am running my Fuel pump with a toggle switch I assumed we would disable the fuel pump on the tune but maybe that still needs to be enabled. Again, not sure just trying to figure out what is different from the EFI live from my HPtune. Thanks again for trying to help.







    1969 Chevelle
    Stock 5.3, twin PTE62/62's
    E85, No intercooler
    Th400, PTC Convertor, 3.90 Gears
    Meth/Water Injection
    Factory PCM, Wiring Harness
    EFILive,V1, Daily Driver

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