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  1. #1

    Default Kubota B21 stalls and dies on throttle up

    I have a 2001 kubota B21 purchased used, with approximately 12,000 hours on the hour meter.

    It has run without issue since I purchased it, running an additional ~ 300 hours on it.

    I recently changed all the filters, and the oil + the transmission/ hydraulic fluids. Subsequent to this maintenance, I used the tractor an additional ~15 hours without issues.


    The Kubota is now exhibiting the following symptoms:

    - Starts and idles OK.

    - When throttling up, the engine will idle at high RPMs for anywhere from 5- 20 seconds and then if not throttled back will quickly lose power and RPMs and eventually die. I am able to keep the engine running by throttling back to about 1/2-2/3.

    - Idling at low RPM seems a bit rough, but not much different then when I first obtained the tractor.

    - Full throttle, while unsustainable as mentioned above, seems to be smooth.



    Caveat: I am a COMPLETE rookie when it comes to tractors, settings, and even basic diesel engine maintenance abilities.



    Thanks in advance for the informed commentary and advice.

    Excellent Forum.
    Last edited by mwolfod; 05-02-2013 at 03:15 PM.

  2. #2
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    Default Re: Kubota B21 stalls and dies on throttle up

    When this was happening to my brother it turned out to be a restriction in the tank fuel pickup...

    Equipment had been sitting awhile and algae started to grow.

    He tired a biocide and it helped.

    Eventually he flushed the tank and replaced filters one last time an no more problem.

    Only a guess on my part.

  3. #3
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    Default Re: Kubota B21 stalls and dies on throttle up

    Sounds like fuel delivery to me also. Start it up and stand on the side where you can watch the fuel filter bowl. Rev it up and see if the bowl is emptying about the time it starts stall. Did you change the fuel filters when you did the others? If so I'll bet it is crud in the tank.

    MarkV

  4. #4

    Default Re: Kubota B21 stalls and dies on throttle up

    Quote Originally Posted by MarkV View Post
    Sounds like fuel delivery to me also. Start it up and stand on the side where you can watch the fuel filter bowl. Rev it up and see if the bowl is emptying about the time it starts stall. Did you change the fuel filters when you did the others? If so I'll bet it is crud in the tank.

    MarkV
    So the bowl should NOT be emptying, if the fuel flow is normal? In other words, the fuel filter should always be full of fuel?

    Yes. The fuel filter is brand new. Are you saying that changing the fuel filter (there is only one (?) from what I understand), may have caused some junk to have gotten thrown to the tank, or that there was pre-existing crud present?


    Also, you guys don't think this is a fuel pump issue?

    Sorry for the uninformed questions, and again, thanks for the replies.


    Much appreciated.

  5. #5
    Elite Member GManBart's Avatar
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    Default Re: Kubota B21 stalls and dies on throttle up

    Even if it's a new filter, you could have gotten a contaminant in the fuel, or disturbed something in the tank, that plugged it up, subsequent to installing the new filter.

  6. #6
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    Default Re: Kubota B21 stalls and dies on throttle up

    Quote Originally Posted by mwolfod View Post
    So the bowl should NOT be emptying, if the fuel flow is normal? In other words, the fuel filter should always be full of fuel?

    Yes. The fuel filter is brand new. Are you saying that changing the fuel filter (there is only one (?) from what I understand), may have caused some junk to have gotten thrown to the tank, or that there was pre-existing crud present?


    Also, you guys don't think this is a fuel pump issue?



    Sorry for the uninformed questions, and again, thanks for the replies.


    Much appreciated.
    Yep, you've got it the filter bowl should stay pretty close to full. There is only one fuel filter and no changing it would not force junk into the tank. Yes there may be existing junk in the tank that has built up over the years. That happened to me on my B21 once. I ended up pulling the fuel line at the filter and draining the tank. I also while draining stuck a clean piece of wood in the tank to stir up any slug or junk that was in there while draining. It does not sound like a fuel pump to me at this point.

    MarkV

  7. #7
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    Default Re: Kubota B21 stalls and dies on throttle up

    12,000 hrs means a lot of fuel has been poured in that tractor, probably not all of it was perfect, could be some foreign matter that has been in the tank, or a bit of water (which stays on the bottom), when you get water in diesel fuel there is an algae that likes to grow in that water and it makes... well... snot is probably the best way to describe it. I would start by draining and flushing the tank, and pull the line at the bowl and blow some air back through it to dislodge any partial blockage as well.


    Ray

  8. #8

    Default Re: Kubota B21 stalls and dies on throttle up

    Thank you for the very informed replies.

    So, if I simply detach the fuel line at the filter, I can drain the entire fuel tank? It is a straight shot from the tank to the filter? Stirring the tank while draining seems like excellent advice.

    How do I go about flushing the tank once it is empty?

    I suppose I could use my portable tire inflator as a source of compressed air to clear the fuel line? I provides enough pressure to inflate my tractor tires.

    Thanks.

  9. #9
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    Default Re: Kubota B21 stalls and dies on throttle up

    Quote Originally Posted by mwolfod View Post
    Thank you for the very informed replies.

    So, if I simply detach the fuel line at the filter, I can drain the entire fuel tank? It is a straight shot from the tank to the filter? Stirring the tank while draining seems like excellent advice.

    How do I go about flushing the tank once it is empty?

    I suppose I could use my portable tire inflator as a source of compressed air to clear the fuel line? I provides enough pressure to inflate my tractor tires.

    Thanks.
    It is a straight shot from the tank to the fuel filter. The pick up for the tank is on the same side of the tractor as the fuel filter. That is where my junk was. If you get things stirred up some fresh diesel will do ok to flush. If you have the stomach for it you can blow through the line. If you start to drain the tank and are not getting a good flow you will know something is blocking the tank intake or the line itself. Good luck.

    MarkV

  10. #10

    Default Re: Kubota B21 stalls and dies on throttle up

    Ok, once the rain lets up, I will attempt these measures and post back with my progress.

    Thanks for all the replies.

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