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Gradall fuel issue. Loosing prime??

Discussion in 'Forklifts/Telehandlers' started by Steve Nichols, Feb 18, 2020.

  1. Steve Nichols

    Steve Nichols Active Member

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    Hello all. I am working on an old gradall with a John Deere power tech 4.5 ser#PE4045H468706.
    Original complaint was it was run out of fuel.
    I am able to get it bleed and have it running strong but after it sits for a couple hours it looses prime and I have to bleed it again.
    In the course of working on it all the supply lines have new seals.
    Is there a check valve somewhere in the system I need to look at?
    I really have no idea where to go from here. Any suggestions?
    Thank you for reading.
     
  2. Delmer

    Delmer Senior Member

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    Any rubber suction hoses? those crack and leak air and then you're screwed, the lift pump won't suck air very well. The lift pump is the most important check valve that I know of, but it could leak back before the lift pump with a suction hose leak. How's the fuel tank? any chicken skin, rust, water? is there a screen in the tank?
     
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  3. Steve Nichols

    Steve Nichols Active Member

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    Good morning Delmar.
    The rubber suction hose from tank to prime pump is brand new.
    Tank appears to be clean, no water / rust. Not sure what chicken skin?
    I suppose it could be the prime pump.
    I assume the lift pump is what I'm referring to as the priming pump? The hand pump right before the water separater?
     
  4. Delmer

    Delmer Senior Member

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    Yes, is this lift/priming pump mounted on the side of the engine, on the camshaft?

    Chicken skin is wrinkled varnish that forms in bio diesel.

    You could try pumping the priming pump before starting, without bleeding it. I don't know how to test the pump without "throwing parts at it".
     
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  5. thepumpguysc

    thepumpguysc Senior Member

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    If the priming pump will come apart, do it & check the valves to see if there’s anything holding them open..
    If not, replace it..
     
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  6. thepumpguysc

    thepumpguysc Senior Member

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    U could try pumping it up before starting it to save crank time on the starter until the new pump arrives.
     
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  7. Steve Nichols

    Steve Nichols Active Member

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    Thanks guys, I'll try the pumping before starting thing.
     
  8. mg2361

    mg2361 Senior Member

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    If you have a water separator filter with a glass bowl, check to make sure the o-ring is between the filter and the bowl. I have seen this mistake made numerous times by customers who changed their filter and not moved the o-ring over creating hard start complaints due to air incursion.
     
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  9. Steve Nichols

    Steve Nichols Active Member

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    Thanks for the tip, except no glass bowl. It's a replaceable filter cartridge.
     
  10. Txhayseed

    Txhayseed Well-Known Member

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    Where your Is your filter head. Pre or post fuel pump ? Get a pair of hose pinch pliers. Run unit and pinch of your main fuel sunction line at what ever it feeds first. Then wait for the time frame your seeing it loose prime. Start the engine and see what happens if your able to start it and dont have to bleed the system you know its bleeding off of the supply side. Do you see any smoke after starting up ? Like maybe you got an injector thats bleeding off ?
     
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  11. Steve Nichols

    Steve Nichols Active Member

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    As a matter of fact I do see black smoke after I get it running. Most pronounced when you aggressively reave the engine.
    I did the crimp test, it would not start. The line was crimped right after the tank, before the filter, transfer pump, and water separator.
     
  12. mg2361

    mg2361 Senior Member

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    Now do the same test with the fuel return line.
     
  13. Txhayseed

    Txhayseed Well-Known Member

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    Black smoke when increasing the rpms quickly especially when your doing several times in a row is normal. Like mg said try the return side and see if you can isolate where exactly your loosing it.
     
  14. Steve Nichols

    Steve Nichols Active Member

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    Thanks for all the replies!
    So, did the crimp test, both the supply and return hoses where crimped. Still no go. Scratching my head how that can be????
     
  15. Vetech63

    Vetech63 Senior Member

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    This is beginning to sound like a different problem. Are you positive that it is losing prime? What exactly are you doing when you attempt to restart this engine after it sits for awhile?
     
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  16. Steve Nichols

    Steve Nichols Active Member

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    I bleed it at the injectors. Grasping at straws here but.......
    I never have bleed the fuel pump where the return line is connected to the fuel pump due to limited access. I bleed it at the bleed screw on the filter/separator. Then bleed the injectors. Do you think I could have a pocket of air trapped in the injection pump? I'm going to get the seals for those two lines (supply & return) where they connect to the pump and try bleeding it. I'm replacing the seals because when I cracked the other fuel lines (at the fuel filter/separator) the seals crumbled and came apart.
     
  17. Vetech63

    Vetech63 Senior Member

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    Its doubtful you have an air trap if your engine runs after you bleed the fuel system. Replaced your lines seals then see what happens.
     
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  18. thepumpguysc

    thepumpguysc Senior Member

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    U still haven’t replaced the supply pump..
     
  19. Steve Nichols

    Steve Nichols Active Member

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    Yes, I changed the prime pump.
     
  20. thepumpguysc

    thepumpguysc Senior Member

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    Sorry musta overlooked that.