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Cummins PT pump problems

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Dino soar, Jan 2, 2020.

Page 2 of 2
  1. Jan 2, 2020 #11
    Dino soar

    Dino soar Road Train Member

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    The engine itself runs excellent. Even starting it on a very cold day, it barely lets out any white smoke. It is remarkable how clean that engine burns.

    I think either dirt got into the pump, or somehow the pump is sucking air. I have no other explanation.
     
    Dino soar, Jan 2, 2020
    Dino soar, Jan 2, 2020
    #11
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  3. Jan 2, 2020 #12
    SmallPackage

    SmallPackage Road Train Member

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    Did you get it rebuilt locally were you can take truck to their shop or ar least take pump back to them to bench test again? Been lucky here San antonio has had a pretty good “hot rod”pump shop for 40 or so years that does all makes of mechanicals. If not i can understand the frustration of having to send it back out again.
     
    SmallPackage, Jan 2, 2020
    SmallPackage, Jan 2, 2020
    #12
  4. Jan 3, 2020 #13
    Dino soar

    Dino soar Road Train Member

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    They are about an hour away. I'll have to get it off in the morning and run it over there and see what they say.

    They told me they would be happy to put it on the stand for me.
     
    Dino soar, Jan 3, 2020
    Dino soar, Jan 3, 2020
    #13
    SmallPackage Thanks this.
  5. Jan 3, 2020 #14
    Dino soar

    Dino soar Road Train Member

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    Here's an update...

    I went out to the garage this morning to pull the pump off and I decided to check each line for tightness just in case before I took it apart.

    When I got to the line that runs to the aftercooler, the fitting felt stiff but I tried to turn it anyway and son-of-a-gun it tightened down further.

    When I put it together I must have felt that stiffness and thought it was tight and didn't want to over tighten it.

    I don't understand how it could have run so well initially and gotten worse but at this point I got all of my throttle response back.

    The only problem now is that if I rev it it seems like it wants to stall as it comes back to idle.

    As @SmallPackage said, maybe I need to just take it out on the road and run it.

    My friend that is a Cummins expert who is away right now told me a while back to just put it on the road and run it and go from there.

    But when I saw that I had zero throttle response like it was before I had the pump rebuilt, that really freaked me out.
     
    Dino soar, Jan 3, 2020
    Dino soar, Jan 3, 2020
    #14
    SmallPackage Thanks this.
  7. Jan 3, 2020 #15
    SmallPackage

    SmallPackage Road Train Member

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    Good deal. So the afc line was loose? It is the diapramn on back of pump to the intake air on aftercooler. It senses boost pressure and adjusts fuel to help control smoke. It well defenantly effect throttle.
    If the “stall”or some call it “gallop” when it comes back to idle does not clear up that is a “fine” adjustment on the throttle shaft.
     
    SmallPackage, Jan 3, 2020
    SmallPackage, Jan 3, 2020
    #15
  8. Jan 3, 2020 #16
    SmallPackage

    SmallPackage Road Train Member

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    Question On the stall/ gallop at return to idle.
    What rpm did they set idle at? I have found that 700-725 seems to be a good idle for my stuff.I know it is too high for some guys taste but It runs smoother and doesn't vibrate and shake the truck so bad as a lower idle tends too. My pump was set at factory spec 650 idle and it idled rougher than the old pump. I set idle up and much better. Helped do away with the gallop too.
    Side note. The old non turbo pumps were set for 500 rpm factory idle. Made them sound good and cammy like a nice engine should but they would shake loose every nut and bolt in the trucks at idle. Cummins bumped up idle on turbo engines to make sure the turbos got good oil flow.
     
    SmallPackage, Jan 3, 2020
    SmallPackage, Jan 3, 2020
    #16
  9. Jan 3, 2020 #17
    xsetra

    xsetra Road Train Member

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    Unless your filter is damaged, no dirt will pass to your pump and cause damage.
    Good to hear you solved problem.
     
    xsetra, Jan 3, 2020
    xsetra, Jan 3, 2020
    #17
    Dino soar Thanks this.
  10. Jan 3, 2020 #18
    Dino soar

    Dino soar Road Train Member

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    Yes the AFC line.

    I think they set it to 700. It idled really slow before they rebuilt it. Sounds much better now.

    Hopefully as I run it the return to idle will be okay. It was perfect when I first put the pump on.

    If it is just a small adjustment I'm sure I could take the truck to them.

    Thanks for the advice.
     
    Last edited: Jan 3, 2020
    Dino soar, Jan 3, 2020
    Dino soar, Jan 3, 2020
    #18
    SmallPackage Thanks this.
  11. Jan 3, 2020 #19
    Dino soar

    Dino soar Road Train Member

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    That's great to hear. I feel better now.

    Thanks for the help!
     
    Dino soar, Jan 3, 2020
    Dino soar, Jan 3, 2020
    #19
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