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Thread: Cat d4 7u smoking and popping louder now

  1. #1
    Join Date
    Dec 2019
    Location
    Columbus, ms 39701
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    44

    Default Cat d4 7u smoking and popping louder now

    Ok, so I've got another question about my 53 model d4 7u. When I bought it about a month ago, it would crank but smoked gray smoke at startup and while running except at full throttle. At full throttle the smoking would stop and seemed very smooth. Well after running it a little, it still smokes but I did notice that cracking the #2 injector would make it smooth out and no smoke. My book says to change out that injector nozzle to clear that up - I did. Seems harder to crank now, smokes probably more than it did, and pops a good bit even at full throttle. I didnt ever drain the fuel out and figure theres water in there but what's up with it smoking and making more racket now? I'm not a full blown mechanic and hope this is not a hard fix if anyone can help with advice? Thanks!

  2. #2
    Join Date
    Nov 2006
    Location
    Faunsdale, AL USA
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    4,169

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    If the #2 pump is not installed with the marked tooth of the plunger gear quadrant aligned properly with the line on the rack, you will get some obnoxious popping. Itís easy to check. Just take side cover off injection pump housing and look in with a bright light. You should be able to compare each pump to the others and quickly see if one is mis-timed.
    D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time

  3. #3
    Join Date
    Dec 2019
    Location
    Columbus, ms 39701
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    Quote Originally Posted by ccjersey View Post
    If the #2 pump is not installed with the marked tooth of the plunger gear quadrant aligned properly with the line on the rack, you will get some obnoxious popping. Itís easy to check. Just take side cover off injection pump housing and look in with a bright light. You should be able to compare each pump to the others and quickly see if one is mis-timed.
    I dont think the pumps have ever been changed on it but I'll check that. I'm just trying to figure how it got worse after I changed the nozzle. Perhaps that was already out of time and I made it worse by it actually getting fuel now. The old nozzle was rusted up badly!

  4. #4
    Join Date
    Nov 2006
    Location
    Minnesota
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    503

    Default

    Exhaust valve stuck open?

  5. #5
    Join Date
    Dec 2019
    Location
    Columbus, ms 39701
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    Could be I guess - how would I check that?

  6. #6
    Join Date
    Nov 2006
    Location
    Minnesota
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    503

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    Pull valve cover and look at the #2 exhaust valve. Is it coming up the same height as the others? Is there any clearance between the rocker arm and valve stem when valve is closed? Listen for a hiss in the exhaust pipe while turning over by hand.

  7. #7
    Join Date
    Dec 2019
    Location
    Columbus, ms 39701
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    Quote Originally Posted by ccjersey View Post
    If the #2 pump is not installed with the marked tooth of the plunger gear quadrant aligned properly with the line on the rack, you will get some obnoxious popping. Itís easy to check. Just take side cover off injection pump housing and look in with a bright light. You should be able to compare each pump to the others and quickly see if one is mis-timed.
    I took off the side cover and took a picture of the pumps. Does anything look wrong?
    Attached Images Attached Images

  8. #8
    Join Date
    Nov 2007
    Location
    NW Ohio
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    Look underneath that sliding rail with the marks on it. The lines should match with the marks on the pump plunger gears. open the throttle then you can move it back and forth to check it, [engine off].

  9. #9
    Join Date
    Dec 2019
    Location
    Columbus, ms 39701
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    Quote Originally Posted by Rome K/G View Post
    Look underneath that sliding rail with the marks on it. The lines should match with the marks on the pump plunger gears. open the throttle then you can move it back and forth to check it, [engine off].
    Ok. I took some more pictures. Looks like they are close?? Is the sliding rail supposed to move freely when the throttle is fully open? I didnt get it to move with my fingers but didnt apply a lot of force.
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  10. #10
    Join Date
    Nov 2007
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    NW Ohio
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    Yes there timed ok. You can move the throttle towards idle but not shutoff position and it should move back and forth. Next would be to check or replace with new injection capsules. Are the rocker arm clearances ok? Head been reconditioned?

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