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Air Intrusion

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Dummy99, Dec 11, 2019.

  1. Dummy99

    Dummy99 Registered User

    Likes Received:
    Nov 21, 2019
    Hey ya'll!

    It's been a few weeks but my issues have returned.

    Symptoms: (Just asking to confirm that this is air intrusion)
    Started truck, idled real rough until dying after about 5 seconds. Would not start after.
    Bled schrader vale, cracked injector lines and got it running.

    Flipped to rear tank while driving but then it throttled up out of no where it then tried to die but I kept it going and flipped back to the front.

    Got home and went to bleed the scharder valve before shutting it off and it seemed like there was no end to the air coming out.

    Truck didn't start next morning.

    I now have the truck in the garage and am pulling out the return lines and will install typ4's return line kit.

    I will also be getting 5 feet of 3/8ths fuel line and 5 feet of 5/16ths fuel line. I was going to go ahed and replace as much of the supply and return lines as possible if the return lines aren't the only thing.

    Am I on the right track? Is there anything I should check? Does it sound like air isn't the only issue?

    Thanks in advance! I hope none of this is too stupid.
  2. dgr

    dgr Full Access Member

    Likes Received:
    Aug 5, 2012
    sac town
    Sounds like your rear tank is out of fuel.

    I suspect that you have a bad fuel pump or maybe a big air leak on the supply side of the fuel pump. Hard to imagine any significant amount of air on a running truck if the fuel pump is working and getting a supply of fuel. Are you sure you weren't hearing a vacuum sound from the Schrader valve?

    Do you have more than 1/4 tank in each tank? Take the line off at the fuel pump that comes from the tank selector valve and see if you're getting fuel there.

    If you have fuel to the pump, pull the fuel filter and crank it over and see if the pump is pumping to the fuel filter head.

    You could also run a line from the IN on the pump and stick it in a 5 gallon can of diesel. That would bypass any tank, hose, selector valve problems.
  3. Randy Bush

    Randy Bush Full Access Member

    Likes Received:
    Jan 2, 2019
    Great Falls, Mt
    After having starting issues with one of my trucks am a real believer in installing a check valve before the mechanical fuel pump. Solved my starting problems.

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