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Thread: 05 LLY starting and surging issues

  1. #1
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    Default 05 LLY starting and surging issues

    Hi guys, i have a 05 lly that im trying to diagnose and fix. It ran great up until about a 2 months ago.

    It cranks over for about 6-8 seconds before it will fire even if i prime the fuel filter before hand. I replaced the whole unit with a brand new one, that shortened the crank time down from about 10 seconds plus.

    Now when i drive the truck if i really baby it it will run smooth through all the gears, if i WOT or try to accelerate (say to pass a car) i get black smoke, no power and surging. Under heavy throttle i have to let off the accelerator to get the truck to shift.

    I have not done a return rate bottle test yet but im sure i know the results, i will get that set up now and test it. I have run a few logs if anyone wants to see them.

    Any other ideas would be greatly appreciated. The truck is totally stock w/ 200k miles


    Thanks guys
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    2005 GMC Sierra ec/lb LLY - stock-

  2. #2
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    whoops, ill try this one might be better help
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    2005 GMC Sierra ec/lb LLY - stock-

  3. #3
    Lifetime Member killerbee's Avatar
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    If this has stock tuning, then you may have some kind of fuel restriction. From the fuel pressure readings, it appears that your CP3 is cavitating. The logs have limited use because you haven't logged most of the necessary PID's.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
    Custom Tuning Services
    DURAMAX/CUMMINS ECM's TCM's for sale, all years, 20% wholesale discount available
    EFILive's first VGT "Software Wastegate Tune"

  4. #4
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    What PIDS would be more helpful? I dont log things very often.

    Think there might be a blockage in the fuel lines or a bad relief valve? The fuel filter and filter housing have hardly any use. Im starting to think i should put a lift pump on to send pressure to the CP3 but if its a different issue i like to solve it first.

    Thanks killerbee
    2005 GMC Sierra ec/lb LLY - stock-

  5. #5
    Lifetime Member killerbee's Avatar
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    Fuel pulse width and throttle position. Your pressure curves don't appear to indicate FPRV opening, that usually looks more like a notch. But I may be wrong.

    If you are having starting issues, then maybe air is getting pulled in. That will kill the fuel pressure.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
    Custom Tuning Services
    DURAMAX/CUMMINS ECM's TCM's for sale, all years, 20% wholesale discount available
    EFILive's first VGT "Software Wastegate Tune"

  6. #6
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    Here are the logs killerbee
    The first one is just start up, second log has a few wfo runs and a few normal runs. I did not get any surging this time.

    thanks again for your time!
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    2005 GMC Sierra ec/lb LLY - stock-

  7. #7
    Lifetime Member killerbee's Avatar
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    MAINBPW is what you need to log for pulse width.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
    Custom Tuning Services
    DURAMAX/CUMMINS ECM's TCM's for sale, all years, 20% wholesale discount available
    EFILive's first VGT "Software Wastegate Tune"

  8. #8
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    Killerbee, ok i think i got it this time sorry for the inconvenience. This test run i got the loss of power but no surging and a rough idle when i went to park it. This has start up and a few runs together.
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    2005 GMC Sierra ec/lb LLY - stock-

  9. #9
    Lifetime Member killerbee's Avatar
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    Dude, I don't have a clue what you have there. This log shows a whole different tune. Your commanded fuel pressure is not even stock. I wonder now if you have some kind of corruption electronically. Codes?

    Being very honest with you, you are going to need to learn how to log what you need. You have nothing useful here.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
    Custom Tuning Services
    DURAMAX/CUMMINS ECM's TCM's for sale, all years, 20% wholesale discount available
    EFILive's first VGT "Software Wastegate Tune"

  10. #10
    Lifetime Member killerbee's Avatar
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    What I do see here (idle roughness) suggests that you are using a very incompetent tune, with a pulse table that was adjusted with a crayon. I would suggest flashing in a stock tune.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
    Custom Tuning Services
    DURAMAX/CUMMINS ECM's TCM's for sale, all years, 20% wholesale discount available
    EFILive's first VGT "Software Wastegate Tune"

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