C12 issue

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Canary379, Mar 10, 2015.

  1. Canary379

    Canary379 Light Load Member

    64
    3
    Apr 13, 2012
    Illinois
    0
    Wanted to post here before I think I may need to take it to the Cat dealer for their diagnosis. Last June had a complete inframe done and things ran good for a while except for black smoke which I was told was going to be there until it brakes in. The black smoke is still there although no where as near as at first. It only puffs a bit of black under acceleration whether under load or not. Even if I am cruising on the expressway and slowly ease into it it will blow a slight trail for a second. Under steady throttle there is nothing. Also when the truck sits over night and if it rains then the next morning when I fire it up it blows out little specs of oil out the stacks. That is my first head scratcher.

    The he next thing is that sometime it doesn't want to start for me in the morning unless I spray it then it fires up. I did pull out the injector harness from the upper rail and from the ecm and found that there is oil in the harness. Looks like there is a bad seal up top where it plugs in and the oil is making its journey down to the ecm. Would this oil cause it to not start and also would it cause a misfire with the injectors? It does sound like the engine is running a bit rough as was wondering if it was the oil in the harness that was causing this.

    It's been a bit agravating since the inframe because these issues should not be. I should also mention I did not replace the turbo at the time of the inframe because a month prior I had rebuilt it with a new cartridge. I did notice the oil supply line under it was covered in oil however.

    Any help or thoughts would be appreciated. Thanks guys. Nick
     
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  3. sshewins

    sshewins Road Train Member

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    Not sure if this will help you, but are you sure those black specs are oil and not soot? I used to drive a 79 mack that would belch the black smoke on command, lol. If it rained overnight, it would spray soot like a swarm of angry bees.

    As far as the oily wiring harness, if you're referring to the connections above the head, from what I've read here that's normal. Not sure to what extent yours is leaking though.

    Wish I could help you more.

    Scott
     
  4. Canary379

    Canary379 Light Load Member

    64
    3
    Apr 13, 2012
    Illinois
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    Thanks Scott.... Now that you said it, I do think it is soot. Which is better than oil I guess. However, I check on 2 friends trucks that have the c12 and their injector harnesses were dry. On mine the plug is wet with oil on both ends, the injector housing and at the computer. Thx
     
  5. KANSAS TRANSIT

    KANSAS TRANSIT Road Train Member

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    Glasco,Ks.
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    We had a bunch of 2003 C-12's overall they were decent, but out of 6 of them we had two that ALWAYS started hard, esp. if it sat longer than a day.

    Had them checked a couple of times and really never found anything? One was so bad you would have to prime the hand pump and give it a shot of starter fluid.
     
  6. Canary379

    Canary379 Light Load Member

    64
    3
    Apr 13, 2012
    Illinois
    0
    I think I may have found my problem for why the truck doesn't want to start and runs like its missing.... The fuel line that runs to the tank that runs from the pump down and along the inside of the left side framerail is leaking diesel fuel every where. Not sure exactly where it is leaking at, but the lines for the air dryer and the suspension where soaked at the end of my work day today.

    I am am not an expert by far, but could this fuel leak be the cause of the truck not starting and running as if it is missing?
     
  7. sshewins

    sshewins Road Train Member

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    Sounds about right. If the pump is losing its prime, it'll probably be hard starting.

    Plus I've heard it said that you should change the fuel lines every 10 years or so.
     
  8. Canary379

    Canary379 Light Load Member

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    3
    Apr 13, 2012
    Illinois
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    well, unfortunately it didnt help any. the fuel line that was leaking was the return line to the tank so the truck still doesnt want to start unless its sprayed.
     
  9. KANSAS TRANSIT

    KANSAS TRANSIT Road Train Member

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    Glasco,Ks.
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    Injector leaking down and losing rail pressure?
     
  10. Slick900

    Slick900 Light Load Member

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    Dec 8, 2009
    Waterloo Ontario
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    I would say the oil in the harness is kind of alarming,,,and a good possibility that's where your problems are coming from!!
    Another stab in the dark would be fuel pressure,,,possibly the pressure is too low,,,or even a chance something has gone haywire and the pressure is too high!!!
    Both the oil in the harness and fuel pressure from sitting overnight could cause a no start the next morning!! My $$$ would bet on a harness issue,,,especially if its saturated to the point its worked its way to the ecm!!
     
  11. Bout Z

    Bout Z Light Load Member

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    Mar 14, 2015
    so. ohio
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    I would suspect the o-rings on the injectors. It could be dumping raw fuel straight into the turbo, and burning out in the exhaust. This would explain the smoke and what you think is specs of oil, could be fuel. This would aldo explain the hard start. After sitting, the injectors and fuel rail will lose prime.
    While the oily harness is a problem, and needs to be corrected, if it were affecting the engine performance it would throw a code to the ecm.

    Hava fine 1...B Z
     
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