Bleeding Air out of Diesel system

Discussion in 'GM Diesel & DuraMax' started by johnkivits, Jan 18, 2011.

  1. johnkivits

    johnkivits New Member

    Hello Chevy fans.

    I'm restoring a 1979 Blazer Diesel but I can't get the air out of the fuel
    system. Can anybody tell me if there's a hand pump or how to bleed the system?

    Greetings John
    The Netherlands
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Im guessing that is the 6.2L diesel. Where is the air at? are your filters bled or just up at the injector pump.
    There is no hand pump on the 6.2L you have to undo the line at the injector nozzle, and bleed that way if it is up top, and if it is in the filter i thought there is a bleed valve there as well? im not 100% since im only used to the mid 80s up 6.2L but bleeding the injectors is the same on them all.
  3. johnkivits

    johnkivits New Member

    Yes, it's the 6.2L,
    There's a bleeding nipple at the top of the filter, schould I start till the diesel
    comes out of the filter?

    There's also some kind of solenoid in the filterhousing, could someone tell me what this is?
    It's a square filterhousing and the filter is mounted with 2 clips.

  4. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Most likely a water separator?
    As to the nipple yes you go till fuel comes out and then tighten it. then if it wont start you have to purge the air via the injector lines.
  5. Joeairforce

    Joeairforce Epic Member 5+ Years 100 Posts

    If it is a 6.2L it's not the original engine for that, since the 6.2L didn't come out until 1982..... If it is a 6.2L someone swapped it in later.... The plugs for the filter base will be for a fuel heater (this is in the top of the base), a WIF sensor (this is near the bottom of the base and just looks like a pole that goes in the filter) and depending on what year the base came from, a vacuum sensor aka a restriction sensor (this will be in about the middle right side of the base only visible with the filter removed).

    The correct way to bleed the air from the filter after a filter change is to pull the wire off the shutoff solenoid on the top of the injector pump (pink wire) and open the bleed screw at the top of the filter and crank the engine until you get fuel out of it, then close it and put the wire back on the shutoff solenoid. Then holding the accelerator pedal to the floor proceed to start the engine. You can lift your foot a little after it starts but maintain it a little until the engine doesn't act like its going to die. If it really doesn't want to start after this then you can do as suggested and loosen the injector lines at the top of the injectors.... but I've never had to do this even after replacing a pump and lines since they will bleed themselves for the most part.
    1 person likes this.
  6. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Thanks for adding Joe. All of my experience comes from working on the MIlitary version of the 6.2L which has different color and type wiring. So the shut off i had forgotten since you usually unhook that when working on the fuel system with these.
    As to the bleeding ive had major problems getting all of the air out after doing an injector pump, and had to do that alot of times by bleeding at the injectors.
    But as usual the civilian version is easier to change.
  7. Joeairforce

    Joeairforce Epic Member 5+ Years 100 Posts

    My experience is from the military side more than the civilian also.... In my experience as long as you unplug the shutoff solenoid before you crank it at all and then crank it until the filter is completely full there should rarely ever be a reason to bleed the injectors... But sometimes these engines will someone else differently than they did you. lol
  8. ghotachevy

    ghotachevy Rockstar ROTM Winner

    Or super chester method can of 100% silicone spray. Keep motor runnin on it till she does on her own
    Last edited: Feb 7, 2011
  9. johnkivits

    johnkivits New Member

    Hey guys, Joeairforce is right. I've mixed up the manufacturing date with another car, i'ts an '86.
    I've bled the system with an unconventional method.
    I've connected a vacuum pump on the fuel filter and pumped till I had pure diesel coming out of the filter. Then I connected the
    vacuumpump on the returnline on the top of the fuelpump while cranking the engine untill diesel came out.
    Connected all the fuel lines again and started with a little bit of throttle.

    Engine fired after 15 seconds!
    Maybe unconventional, but it works!
    Thanks for all the support and maybe speak to you all later while rebuilding al the lights, interior and connecting all the wires.

  10. Joeairforce

    Joeairforce Epic Member 5+ Years 100 Posts

    That's sure one way to do it. Good to hear ya got it running.

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