Help on my Cummins QSD 4.2L

Discussion in 'Surface Drives' started by danukon, Jun 4, 2015.

  1. danukon
    Joined: May 2015
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: washington

    danukon New Member

    Hello everyone, I'm new here on forum and I need your help.
    I have a Cummins QSD 4.2L that knock at 1450 -1500 rpm. At the last service, they have completely overhauled the engine, replaced one injector, replaced the camshaft on the valve train. Still have the same exact noise as before and the men from service said they found no damage in pistons, pins, cannot figure it out.

    Somebody told me to use a dish tool to cut out injectors,and if i need to isolate the cylinder that has the knock, it sounds like an injector causing the issue once I can isolate swap the suspected cut injector with another cylinder, all injectors should be changed at time of overhauls. Or I'll risk damage to the overhauls engine. I know that an injector only has a life span of 500,000 miles.

    Do you think is too difficult? What you recomend me, to buy the service manual for my truck [TradeBit.Com] and to save money by repairing it myself, or you recommend me to go on a proffesional service and to solve this problem.

    Thank you for your attention!
  2. gonzo
    Joined: Aug 2002
    Posts: 16,565
    Likes: 1,555, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    If you loosen one injector pipe at a time, the knock will disappear if there is a mechanical problem in that cylinder. For example, a worn wrist pin of rod bearing. A bent rod can also cause a problem. In general, worn injectors open at a lower pressure and inject fuel that is not completely atomized. The result is a lot of black smoke.
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