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Thread: 03 rpm's fluxuating,hesitating, stalling...need help

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  1. #1
    Join Date
    Mar 2015
    Location
    MI
    Posts
    8

    Default 03 rpm's fluxuating,hesitating, stalling...need help

    a few days ago my truck seem to be hesitating a little, but would run fine on highway. i found a pinhole in a return fuel line that runs from top of fuel cooler back to tank. for the time being i cut out the bad piece of line and replaced with hose. I also changed the fuel filter as well. filter filled with fuel when priming. once that was done, i had a hard time getting truck started again, (it would start/run for about 30 seconds or so then stall) trying to get any air out of the lines. as i primed the fuel filter, i was pumping a lot of air. the primer is working ok, if i pump fast enough, maybe 2 pumps per second, the air bubble would stop as the filter would fill completly with fuel and only spray out fuel, except i could never get the primer so hard that i could not push it, i could just keep pumping. then what i tried was prime the filter then turn the key to the run position thinking i was basically 'priming' the injectors/fuel system (but i could be wrong about that). i did this three times, prime the filter, turn the key to 'on' and keep priming, then turn key off, prime, turn key on, keep priming filter etc. the last time i did this, i started the truck, as the truck ran, i continued priming, this time the truck continued to run. i stopped priming the filter, and the truck continued running. i let it idle for about fifteen minutes or so then took it up/down the road a couple of times with no issue. after the short drive, i was then able to prime the filter to the point i could no longer pump. i also noticed the rpm's fluxuating at idle, while it was hard to see any change in the rpm needle, i could hear it.
    i also had three codes come up: P0571, U1041, U1024. i cleared those codes (since the truck was running again) to see if they would come back. U1024 was the only code that came back. i cleard that code again a couple days ago and now no codes are coming up any longer. one other thing happening is that it is cranking longer before it will start. normally i would say 1-2 seconds to crank to start, now it will crank 3-5 seconds but not start, turn key off, crank again 2-4 seconds and it will start. i took it for an hour drive last night and had no issues, it started normally (normal crank time) and do not remember hearing rpm's fluxuate. after sitting for over an hour, i had to crank it twice to get it started, then could hear the rpm fluxuate and noticed for a few seconds that the idle rpm's dropped to around 500. i pushed the accelerator and the rpm's came back up to normal, but i could hear the rpm's fluxuate again. drove it home (hour drive) at highway speeds, 60-75 and had no issues. this morning had to crank twice to start it, but then it stalled out. primer was easy to push. i opened the bleeder screw and only fuel came out. tried priming again with bleeder closed, but could not primer would not get hard to pump. i got the truck to start, but it stalled out. sorry for the long post, but wanted to give as much info as i could. any thoughts/ideas as to what might be happening? 148k on the truck. thanks for any ideas anyone could provide. --Brian

  2. #2
    Join Date
    Mar 2015
    Location
    MI
    Posts
    8

    Default additional information

    i opened the bleeder screw and more air came out. i tried to prime several times, each time i opened bleeder i got air. primer will not get any harder to prime. maybe another leak in the fuel line somewhere? will try pressurizing the tank today.

  3. #3
    Join Date
    Dec 2002
    Location
    Teton Valley, Idaho
    Posts
    1,873

    Default

    If you've already found a return line to have a hole in it (weeping fuel?) my first guess would be a supply line with the same problem. Won't be easy to find because that line is under a relative vacuum so would be drawing air into the fuel system rather than visibly leaking fuel. Pressurizing the fuel tank (only a few PSI) might show where the leak is, but I'd also start saving some $$$ to install a lift pump.

  4. #4
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    In the long game what you really need is a lift pump. This will push the fuel to the filter and keep it full of fuel and not air. A lift pump will not fix your leak(s) but it will help you find them. It is often the filter head. A simple oring rebuild kit is all you should need for this part. Then check again for leaks.

    The rolling/surging idle could be caused by aerated fuel.

    Also it is my suggestion that you not use the plastic (Wix-Napa-Car Quest) fuel filters, only a good metal one. The plastic ones have been at the root of many calls of distress cured by simply replacing with a higher quality unit.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
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  5. #5
    Join Date
    Mar 2015
    Location
    MI
    Posts
    8

    Default

    i pulled the hose off the inlet to the fuel filter and pressurized the tank, seems it took about a minute or so for a very small stream of fuel to come out. put the hose back on and found another leak, this one coming from the supply line at the front of the tank, dripping from the quick connect.

  6. #6
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    When we install our lift pump kits we start at the tank sender (plastic) and replace the first section of hose completely. Not sure why yours would be leaking as they seldom do, but good to replace it and get the system under pressure.

    http://www.kennedydiesel.com/docs/Ba...stallation.pdf
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  7. #7
    Join Date
    Mar 2015
    Location
    MI
    Posts
    8

    Default

    well i bit the bullett yesterday and ordered a new set of fuel lines from the dealer. my fuel lines seem to be rusted at each point where they snap in to the plastic clips. seems to worse back by the fuel cooler. $483 plus tax from the dealer. it sounds like its a complete set, supply, return, cooler line, lines from tank and the two short tubes that screw in to the cooler. i'm going to tackle this job myself. anyone done this job before and anything i should look out for? anyone recommend a coating for these lines to stop/slow the rust? was going to order from linestogo.com, but found some links with google that made me think twice about ordering from them.

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