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Caterpillar running rough

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Austinvohs1996, Jul 25, 2021.

  1. Jul 25, 2021 #1
    Austinvohs1996

    Austinvohs1996 Bobtail Member

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    HELP!!!
    Caterpillar 3176 in 1991 Pete 357
    This problem started a couple a months ago. Started happening every so often and now getting worse. I’ll get a engine light and truck misses for a second and comes right back. Only thing I can think of is fuel delivery issue like air getting sucked from somewhere or wiring issue. When this first started it was random throughout my day. Happening very lightly. Now it seems to be happening worse and very harshly. Seems to happen a lot more in the morning. Specifically about 10 or 15 mins after start up. I’ll let the truck warm up for a few and it will start missing and throwing a engine light. Gets worse after leaving the yard for about the first half hour of my morning then seems to go away and run fine all day long.
    I’ve taken it to two mechanics already and they can’t find any stored codes and they’re not able to diagnose it because of how intermediate the problem is. I’ve changed fuel filters , ran injector cleaner , changed out the muffler.. batteries are good. Truck doesn’t smoke… Can’t find and loose grounds. Don’t know what else to do.
    NEED HELP
     
    Austinvohs1996, Jul 25, 2021
    Austinvohs1996, Jul 25, 2021
    #1
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  3. Jul 25, 2021 #2
    truckdriver31

    truckdriver31 Road Train Member

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    maybe the ecm.. my buddy's cat/pete did the same. cold start run like sheetz for 30 minutes. then run fine. it turned out to be his ecm.
     
    truckdriver31, Jul 25, 2021
    truckdriver31, Jul 25, 2021
    #2
  4. Jul 25, 2021 #3
    bad-luck

    bad-luck Road Train Member

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    1st thing that comes to mind is a bad injector. I would either get a Thermo heat gun and check temps on all the cylinders when it is missing, they should all be about the same temp, the one that is not is you culprit. Or unplug the injectors one at abtime. When you unplug an injector and your miss goes away, you found the bad injector.
     
    bad-luck, Jul 25, 2021
    bad-luck, Jul 25, 2021
    #3
  5. Jul 25, 2021 #4
    SWMO_Transport

    SWMO_Transport Bobtail Member

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    Definitely use the heat gun trick. Sure fire way to diagnose a poo poo injector
     
    SWMO_Transport, Jul 25, 2021
    SWMO_Transport, Jul 25, 2021
    #4
  7. Jul 25, 2021 #5
    Austinvohs1996

    Austinvohs1996 Bobtail Member

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    Also forgot to mention there is a small diesel leak at the bottom of the ecm. Don’t know if that would be causing the issue
     
    Austinvohs1996, Jul 25, 2021
    Austinvohs1996, Jul 25, 2021
    #5
    Magoo1968 and truckdriver31 Thank this.
  8. Jul 25, 2021 #6
    BoxCarKidd

    BoxCarKidd Road Train Member

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    Things are not the same as they once were. People got divorced and it was done. Now they get remarried and or just shack up. Some live happily ever after or not.
    Point being a piece of paper does not fix the problem.
    What is the code that goes with the check engine light?
    Many loose the thought of what would cause this if there was no computer. Sight glass in fuel line to check for air is a good start.
     
    BoxCarKidd, Jul 25, 2021
    BoxCarKidd, Jul 25, 2021
    #6
    spsauerland, Magoo1968 and AModelCat Thank this.
  9. Jul 25, 2021 #7
    BoxCarKidd

    BoxCarKidd Road Train Member

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    What is your fuel pressure off the filter head when it is mucking up?
     
    BoxCarKidd, Jul 25, 2021
    BoxCarKidd, Jul 25, 2021
    #7
  10. Jul 25, 2021 #8
    AModelCat

    AModelCat Road Train Member

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    If the engine light comes on, there should be a fault associated with it. CAT is pretty good about logging every event a fault code. The shops that scanned it, did they give a printout of the logged faults and events? Where the using CAT ET to read the ECM or just a generic scan tool?
     
    AModelCat, Jul 25, 2021
    AModelCat, Jul 25, 2021
    #8
    spsauerland Thanks this.
  11. Jul 26, 2021 #9
    Magoo1968

    Magoo1968 Road Train Member

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    That ecm is cooled by fuel .. it’s possible that leak is allowing air into fuel system. Mr Haney told a member to bypass fuel line and put a stand-off behind ecm to move it away from the block to allow airflow behind it.. ecm is unrepairable if leaking fuel and expensive. If you get a year or 5 extra with his fix it seems worth it.
     
    Magoo1968, Jul 26, 2021
    Magoo1968, Jul 26, 2021
    #9
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  12. Jul 26, 2021 #10
    spsauerland

    spsauerland Road Train Member

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    Small fuel leak= lose of fuel prime, hard start, and white smoke.
     
    spsauerland, Jul 26, 2021
    spsauerland, Jul 26, 2021
    #10
    BoxCarKidd, Magoo1968 and Oxbow Thank this.
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