rough running, about to sputter out

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by stonefly4, Nov 10, 2019.

  1. stonefly4

    stonefly4 Light Load Member

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    I know, right?

    I do not understand the fuel system on this truck. I don't know whether I was getting a vacuum or the opposite—too much pressure. I wish I'd had a fuel pressure gauge. I'd be way money ahead if I had one. I got one now.

    In my searches, I did read that too high fuel pressure in the fuel rail could cause the injectors not to fire, that the ECM would read the high pressure and shut off the injectors.
     
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  2. Rideandrepair

    Rideandrepair Road Train Member

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    I’ll have to remember that one,glad you got it fixed without spending a bunch on Diagnostics, could have cost a lot, even with honest well meaning Mechanics.
     
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  3. Rideandrepair

    Rideandrepair Road Train Member

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    My Truck will be done Monday, Cac was shot, got just about everything new now. It’s amazing how long the Detroit lasted. At least 1.3 mil on an OH. Valve guides were so worn, the valves had hit pistons on 3 cylinders.Tiny marks on them. But it still ran!!
     
  4. Rideandrepair

    Rideandrepair Road Train Member

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    I pressurized the tanks once, after changing an injector, had lost prime, it started ran about 30 seconds, shut down, till I let the pressure bleed off. So it must be true. My guess is the cap vent created a vacuum. I don’t know how it would cause excessive pressure. I’m definitely getting a fuel pressure gage, after reading your experience. New speedometer and pyrometer now, for starters.
     
  5. stonefly4

    stonefly4 Light Load Member

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    Glad your truck will be ready to work.

    Series 60 is a good engine. Mine is closing on 2 million with original bearings and never had the head off.

    It still runs great after sitting for 5 years without turning.

    Oil pressure is low, however. I'm fixing to replace the bearings. I started another topic asking for advice on torquing the mains.
     
    Last edited: Jan 19, 2020
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  6. Scooter Jones

    Scooter Jones Road Train Member

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    You're in the $$$ again!
     
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  7. stonefly4

    stonefly4 Light Load Member

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    I don't understand either, unless the return fuel causes a pressure buildup.
     
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  8. stonefly4

    stonefly4 Light Load Member

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    Maybe pressure builds up because return fuel spills into the tank hotter than the fuel that leaves the tank.
     
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  9. lwlevens

    lwlevens Medium Load Member

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    I would say to much fuel pressure. If you really want to find out put the old caps back on... if you dare.
     
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  10. stonefly4

    stonefly4 Light Load Member

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    haha...

    Noooo... I believe I'll leave well enough alone. At my age, I've learned to leave some mysteries to remain just that... mysteries!
     
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