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Cummins QSX15 Smoking

Discussion in 'Shop Talk' started by trackdoc, Sep 16, 2014.

  1. trackdoc

    trackdoc Well-Known Member

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    Hi there, I have a QSX15 Cummins with 6000 hours on it in a John Deere forager.
    Over the last 2 seasons it has started to blow a constant haze of black smoke.
    I have checked the cam timing, set the injectors and valves (2 times), changed the intercooler, done the injector cut out and found number 2 was a little weaker than the rest.
    Installed a new injector still smoking.
    I have 28 psi of boost, and 280 psi of fuel pressure when in a heavy stall.
    Installed a new turbo.
    The engine is running fine and I would not say it is down in power very much, but it aint as sharp as it used to be.
    It is weird in that it won't smoke all the time, some days no smoke and others it will haze when under a light load.
    The ECM software is standard, we have owned this machine since new and it has never been messed with.
    O nearly forgot, ambient temp/ press sensors new, inlet manifold temp/press sensor new.
    The thing seems to be over fueling a little, I would say she is using a little more fuel than she used to.
    I know a lot of people would say to fit a full set of injectors, but would like to hear from people who know this engine.

    Thanks
     
  2. trackdoc

    trackdoc Well-Known Member

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    Forgot to say, engine is 2003 no egr
     
  3. Mobiltech

    Mobiltech Senior Member

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    I'm not sure what the spec is for fuel pressure but 280 sounds high. Cat runs about 90 psi. If it's high I would be checking return lines for blockage.
     
  4. trackdoc

    trackdoc Well-Known Member

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    This engine has the HPI fuel system, I actually thought the pressure was a little low, I have also changed both fuel regulating valves.
     
  5. Deeretracks

    Deeretracks Senior Member

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    Fuel pressure seems ok. Spec is 255-290psi @ 2100rpm. Does your model have the filter screen in the lift pump. I've seen them partially plugged. Mostly on Genset's though.
     
  6. trackdoc

    trackdoc Well-Known Member

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    The only screen I have ever seen is the one where the feed enters the 1st filter housing.
    Is there a screen on the electric lift pump too ?
     
  7. Deeretracks

    Deeretracks Senior Member

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    Depends on what style. If the lift pump is mounted on the integrated fuel system module then there is no screen. If it has an external lift pump then there should be a large allen head plug with a screen behind it.
     
  8. partsandservice

    partsandservice Senior Member

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    I would look for an intake air restriction , or a leak or restriction in the air to air.
     
  9. trackdoc

    trackdoc Well-Known Member

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    Already been there, but thanks.
     
  10. RZucker

    RZucker Senior Member

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    Have your camshafts been checked with the proper timing wedges to see if the cam gears have slipped? Have they checked the rocker rollers for slop. Both of those issues will retard injection timing on the QSX/Isx engines. 28 PSI boost at full stall sounds a bit low too.
     
  11. trackdoc

    trackdoc Well-Known Member

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    Hi there, yea I purchased the pin and wedges from Cummins and both cams where spot on.
    I have not checked the rocker rollers though.
    Thanks
     
  12. overworked

    overworked Senior Member

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    Are you shure that you have a engine problem? Seeing as its getting worse season after season, could be after engine.
     
  13. overworked

    overworked Senior Member

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    Have you tried cylinder cutout under working conditions to see if smoke clears up?
     
  14. trackdoc

    trackdoc Well-Known Member

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    Yea, sure it is engine.
    The processing end of the machine is rebuilt every winter
     
  15. trackdoc

    trackdoc Well-Known Member

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    No not tried that, would kinda not like to cut out a cylinder under full load.
    I am 20 years a Cat mechanic, and have never done this, don't like to cut out a cylinder when there is an unstable load on the engine and the rpm is not constant.
    Woud you advise this on a Cummins ?
     
  16. overworked

    overworked Senior Member

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    You might want to get the other injectors tested, they might be dropping too much fuel to soon.
     
  17. trackdoc

    trackdoc Well-Known Member

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    Yea I agree on that one.
    Problem is I have never in my life taken injectors or pumps to a diesel shop where they have not found a problem that costs $$ to repair.
    I wouldn't mind but after spending $$ I find out that the engine is running no differently.
    So hence I am very sceptical about getting them tested, I would bet $$ they would all require rebuilding, and when refitted the problem could still be there.
    I was kinda hopeing someone on here would have mentioned timing actuators and gone down that route, but I guess I will have to start with a full set of injectors
     
  18. partsandservice

    partsandservice Senior Member

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    Sounds like you have covered well, so just things to ponder. Injectors with a weak spray pattern would not cause a black smoke so I am with you about doubting the injectors . It comes and goes, what about VGT position not holding commanded position but still within low and high range. Would new turbo need to be calibrated? Parasitic load? If not in processor , any hydraulic piston pumps on that machine ? A piston pump could hanging on stroke. Keep in mind I know nothing about a forager. Engine wiring harness esp between boost sensor and ECM, boost sensor could stick high and not code if it is with in parameters. Would have to check this while sensor is hooked with a break out harness or by piercing the wire. I don't understand what you mean about timing actuators, correct me if I am wrong but would injection timing not be simply controlled by the ECM with input from engine position sensors. I think engine wiring harness.
     
    Last edited: Sep 18, 2014
  19. trackdoc

    trackdoc Well-Known Member

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    Hi there, this engine does not have a VGT, it has a waste gate.
    There is def no parasitic load on the engine.
    The boost pressure readings rise and fall with the engine load, I have spend a little bit of time in the cab watching this while the machine has been working.
    From what I gather think the timing actuators control when fuel is delivered to the engine. There are two timing actuators , one for cylinders 1, 2, and 3 and one for cylinders 4, 5, and 6.
    As I said before, I am not overly familiar with this engine, I wonder if these actuators can cause a timing advance/retard ?
     
  20. Nige

    Nige Senior Member

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    If Cummins Insite has the same capability as Cat ET to perform a cylinder cutout test then that's the first thing I'd go for, just to see if you maybe have a lazy injector.