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Thread: Can't get this right

  1. #41
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    I dont know the actual fuel pressure, the main fuel system is the stock in tank pump supplemented by a second pump connected directly to the fuel rail that is pressure referenced to kick in at a certain point usually around 2-3lbs of boost pressure.
    I would not know how to read fuel pressure when you have two fuel systems in operation. I do have a light mounted in my pillar gauges to tell me when the second pump is in operation.
    The MAP sensor was calibrated to read the same as the stock sensor with key on and engine off. It took several tries but it is the same as stock in the last tune that I posted.

    Thank you again,
    Greg

  2. #42
    Senior Member Chuck L.'s Avatar
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    Talking My $.02..

    Quote Originally Posted by eclispe1 View Post
    I dont know the actual fuel pressure, the main fuel system is the stock in tank pump supplemented by a second pump connected directly to the fuel rail that is pressure referenced to kick in at a certain point usually around 2-3lbs of boost pressure.
    I would not know how to read fuel pressure when you have two fuel systems in operation. I do have a light mounted in my pillar gauges to tell me when the second pump is in operation.
    The MAP sensor was calibrated to read the same as the stock sensor with key on and engine off. It took several tries but it is the same as stock in the last tune that I posted.

    Thank you again,
    Greg
    1. Using the stock pump: The stock fuel pump may be
    "outrun" by the added inline pump. Doesn't the stock pump have the regulator in the tank w/ the pump?
    Do you know if the stock system is working?
    If the stock pump can't keep up w/ the add-on pump, the system is not going to work correctly. [Low volume].
    2. Just because you see the lite on, does not mean the 2nd pump is working. Depending on where you are feeding the lite power,all it may be telling you is, that the relay is being powered. [The inline pump IS on a relay, and the stock pump is hotwired, right??]
    3. Until you get a fuel press gauge on the rail, you cannot troubleshoot the system. A rail connection will tell you if the 2nd pump is working, or not. It will also tell what the real pressure is.
    4. You can hook up a fuel press ga w/ a hose long enuf to put it under the wiper arm. This way you can see what the psi is while driving.
    5. To test the 2nd pump: W/ eng running, trigger the 2nd pump, watch the ga.. 2 pumps running at idle, should bump the psi.
    6. Are you using a second pressure regulator? How is this system controlled?? Is the intank, oem regulator the only 1 in the system? If so, we need to get the fuel flow under the control of one regulator.

    Bottom line: U R "pounding sand in a rat hole" until you get a handle on the fuel system.. No amt of tuning is going to resolve your problem until you do that.

    HTh,
    Chuck L.
    CODY Motorsports
    Fuel Injector Service
    Madison, GA.
    706-342-3152
    770-265-5144 [C]

  3. #43
    Lifetime Member johnv's Avatar
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    would probably be better just replaceing the intank pump with a walbro and leaving the factory regulator inplace ,
    then do away with the second inline pump as it will cause a restriction in line when not running and fuel pressure will be uncontrolled when it is.
    Back yard boost
    347+ T76 = 770 rwhp 10.96 @ 135 mph

  4. #44
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    The stock fuel system is bone stock, no hotwire mod yet. I thought the regulator was on the fuel rail on the F body. I have the light wired to the hot side of the pressure switch after the relay and have jumpered it to test it and it is working perfectly as you can hear the pump kick in and see the fuel line move as it is pressureized with or without the car running. I'm pretty sure that the FMU controlls the pressure of the second pump, it came with the supercharger kit just for that purpose I would assume. I will try to get a gauge in the next few days to get some readings on the pressure. In the meantime I will try the auto ve one more time to see if I can get it closer. I'm out of money now and can't really afford to try anything else that requires a purchase for a little while.

  5. #45
    Lifetime Member johnv's Avatar
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    If it is a rail mounted regulator you should be okay.
    Back yard boost
    347+ T76 = 770 rwhp 10.96 @ 135 mph

  6. #46
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by eclispe1 View Post
    ...
    I thought the regulator was on the fuel rail on the F body.
    ...
    You mean stock LS1 F-body...?...no it's in the tank...

    When you look at your fuel rail, you will see a can-looking thingy connected to the fuel rail crossover tube...

    Two clues:
    - does the can-looking thingy have an air hose going to the manifold...?
    - does the can-looking thingy have an additional fuel line connected with a threaded union/nut...?

    Look closely at it... on the stock F-body that can-looking thingy is the pulse dampner (and not the FPR)... it has no manifold air hose and no return fuel line... you should see only one fuel line going to the rail.

    Do you have any pics...?

    Edit: See attached diagrams of fuel rail, which one do you have...?

    Dampner: IFR has to be sloped.
    Regulator: IFR has to be flat.

    If you have an aftermarket regulator, it will look different, be in a different location, but it will have all of these: fuel line (in), return line (out), reference air hose.

    In both cases you need to measure rail pressure.


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    Last edited by joecar; March 20th, 2010 at 09:57 AM. Reason: Pink and Red are too close, changed Pink to other color

  7. #47
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by johnv View Post
    If it is a rail mounted regulator you should be okay.
    If he has a rail mounted FPR (i.e. manifold-reference, return line), then his IFR table is wrong (it is sloped).

    From what he said, it seems he has the stock FPR in the tank (no manifold-reference, no return line), in which case it is correct that his IFR is sloped... (but does his IFR match his rail pressure and injectors...?).

  8. #48
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    You are correct there is no return line or air connection, I just assumed that thing was thr fpr I guess you can tell that I'm not a mechanic! I'm dead broke right now and pending loss of employment so it will be awhile until I can get the fuel pressure readings. I will try the last tune posted and see how close I can get it. I might put the slicks on and go wild until I have enough data to finish the tune today.

  9. #49
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    We had a great day here in Florida and I got some data. I will post the two logs and the tune file. It seems to run really well except when you let off of the throttle it goes pig rich. Then when you first get on the throttle after letting off it goes way lean to the point that the car will buck a little then go. It did stall at idle several times while I'm sitting at lights.
    Attached Files Attached Files

  10. #50
    Lifetime Member johnv's Avatar
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    Your fueling seems to be all over the place at low MAP and rpm,Where is the wideband sensor located ? any exhaust leaks ?

    I'm wondering if you maybe have similar operating system problem to this thread - http://forum.efilive.com/showthread.php?t=13235

    also when i look at your Ben map from logs you seem to have alot of cell count hits in the 0-400 rpm row, yet when looking at the log you don't actually dip into that rpm range to often.

    You really need to verify what fuel pressure you have and weather its fluctuating much esp when the second pump cuts in to enable IFR to be scaled correctly.
    Back yard boost
    347+ T76 = 770 rwhp 10.96 @ 135 mph

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