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Kubota ZD21 Black Smoke

Discussion in 'Mechanic and Repair' started by shwoogee, Aug 15, 2006.

  1. shwoogee

    shwoogee LawnSite Member
    from pa
    Posts: 3

    Hopefully someone can help. For a few weeks now my Kubota has been blowing black smoke and losing power off and on. I call dealership pick two fuel filters, drain fuel, replace with fresh fuel, bleed the system and they also suggest running without the air filter for a little while. did all of that and it's still blowing black smoke. any ideas/suggestions
  2. mowerman90

    mowerman90 LawnSite Bronze Member
    Posts: 1,491

    whomever told you to run without the aircleaner is an "IDIOT":hammerhead:
  3. mjohnson1

    mjohnson1 LawnSite Member
    Posts: 76

    im pretty sure black smoke usually means air/fuel mixture is too rich, which would explain the no air filter, but still that is terrible advice. is the carb adjusted correctly? you might try reposting in the mechanic and repair section if this doesn't get moved. lawnmaniac883 seems to know alot.
  4. FordManKubotaDreamer

    FordManKubotaDreamer LawnSite Member
    Posts: 90

    I just read the manual and it says.

    Black smoke ...causes...
    Fuel quality is poor
    Too much oil
    Engine is overloaded

    Inside exhaust muffler is dumped with fuel
    Injection nozzle trouble
    Fuel quality is poor
  5. qps

    qps LawnSite Bronze Member
    from Indy
    Posts: 1,484

    That sounds like a fuel filter problem I had last season, must have sucked some crud into the injectors...if changing filter didn't fix it..
  6. twj721

    twj721 LawnSite Senior Member
    Posts: 619

    Hope you got this on a voice recorder so when they say you engine is dusted because you run it without the airfilter and thus that is abuse and that thus voids you engine warranty not saying that it will come to that but it could happen .And if this idot calls himself a shop foreman Find you another dealer that knows about diesel repairs and KNOWS THAT YOU DO NOT RUN ANY ENGINE WITHOUT A AIRFILTER :hammerhead: :hammerhead:
    Good luck and hope that you find your problem and thta it is something simple and easy to fix, Twj
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Hmmm, OK maniac the floor is yours dude.....
  8. DEEJ

    DEEJ LawnSite Member
    Posts: 230



    Careful on the advice there - because it is wrong! Snowblowers come stock with no air filter. Snowmobiles come stock with no air filter.

    That said, I do agree 100% that no air filter on a mower is absolutley wrong. Dust and dirt are a number 1 killer of small engines.

    Is this ZD21 gas or diesel. I am not sure that was stated. Either way, black smoke = running rich = too much fuel or not enough air.

    And, to set the record straight ... you want quality help and advice, Restrorob is you man - ask the best, get the right answer :) Geez, that oughta make up for any of my past sins against him!! Hey Rob!! :canadaflag:
  9. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    *steps onto the floor infront of large crowd, legs shaking, face turning red; looks over at rob who happens to be laughin his arse off*

    Ahh what the hell.

    Black smoke is caused by too much fuel being injected into the engine. Since you dont see white smoke that eliminates the injector stuck open possibility.

    Is your fuel clean and not bought from a station that moves 15 gallons of diesel a month? I would dip the tank real quick and make sure your diesel isnt murky or green for that matter.

    Second, how much smoke are you talking about here? Blacking out the street :cool2: kind of smoke or light haze while mowing?

    That said I dont know much about small diesels on lawnmowers, bring me a large truck or marine diesel and we can talk but 21hp diesels arent necessarily my fortay.

    *motions for rob to come on stage*
  10. tomo

    tomo LawnSite Senior Member
    Posts: 660

    1/check all basics fuel cleanliness etc
    2/change fuel for known clean fuel
    3/flush out fuel lines--clean out tank
    4/change fuel filter
    5/rectify fuel leaks or any minor weeps
    6/change air filter if dirty
    7/power balance test
    8/ injector pump timing check
    9/compression test wet dry
    10/check 4 blown head gskt[pressure test cooling system]
    11/have injectors sericed - check result
    12/have injector pump serviced check result
    In summary this method of diagnosis has always worked for me .

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