KX 121-3 S Series Bogging and stalling issues

[Land Warrior]

I am having issues with a Kubota KX121-3 S Series Mini-Ex. (2200 hours) the machine was parked for 3 weeks and not started but was running great when I last shut it down. The next time it was started it started perfect and idled fine while it was warming up. Then as I started to drive it started bogging down and sounded like the engine was about o die. I let off the forward controls and the engine smoothed back out and seemed okay. I checked the fuel gauge and it was at 3/4 tank. I was starting down a hill so thought it may have been about out of fuel which is what it sounded like. I managed to baby it down off the hill to a lower area to do some work and it seemed to get better as the machine continued to warm up. However when I when to use the bucket it would almost die again. Actually any hydraulic commands would cause this including forward or reverse. It did this three or four more times and then it cleared up and ran perfect the rest of the time I used it that day Approximately 4 to 5 hours work time. The next day I went to use it again and this time it would not clear up and run no matter how long I let it warm up. I finally shut it down.

A couple days of sitting once again due to rain, I purchased a new OEM fuel filter from Kubota. Also purchased diesel fuel additive that was supposed to remove any water, slime or algae from tank and also was supposed to clean injectors etc. ($20 + per bottle.) I added the prescribed amount of additive to the fuel tank. I then removed the sediment bowl and cleaned it out. There was no water in the bowl at all, but had a tiny amount of what looked like dirt possibly in bottom of it. I then removed the air filter and inspected the (outer air filter) It had some dust in it that I was able to tap the filter and it seemed to knock it out and I stopped when no more dust fell out then replaced it and reassembled the filter canister.

I then tried to start the machine and the sputtering and bogging down started immediately. I decided to let it run for a longer period of time to let the fuel additive and cleaner have time to work through the fuel system but it never cleared up. The machine with no load and at idle or even with the throttle up to mid-way it made no difference. It will run perfect then suddenly start to miss, sputter, shake and then almost die, puffs of black/white smoke come from exhaust, then clear up run perfect. After a few seconds or at times even 2-3 minutes o running perfect it will again go through the sputter event again. Doing this over and over no matter if engine has warmed or not. So....What else can I possibly check and also if it's an injector pump is there a way for me to check this to be sure without special tools etc. before purchasing one.
Additional Info:
I can hear the fuel pump and it sounds consistent as far as the sound it makes it doesn't appear to slow down or speed up. Although I haven't taken any lines off to ensure this flow is steady. I also haven't blead the system simply because when I researched how to change the fuel filter it was only recommended that the fuel shut off to the fuel sediment bowl (a clear see through bowl with a red ring that floats when water is present) then to wipe down the area around the filter prior to removing the old filter, then to fill the new filter with clean fuel and reinstall filter. Next turn the sediment bowl shut off back on and to turn key switch on for a few seconds before trying to start the engine. This was the prescribed way I found to "Prime" the system after fuel filter change and sediment bowl clean out. I cannot find a procedure online for actually bleeding the fuel system.

I have also pulled the parts schematic for the fuel system for this machine up online and according to Kubota's drawings that I found the prints have print item numbers for replacement purchases etc. There is a total of two filters. (not counting the sediment bowl) One was actually a strainer that is at the fuel tank entry. I would actually call this a fuel strainer rather than a filter but okay whatever....Potato, potatah. The other is the actual metal screw on filter. It is like the oil filter but smaller and silver with Japanese writing on it. If there is another filter somewhere in this fuel system Kubota failed to show this in their documentation.

Any help figuring out what to purchase or do to repair is greatly appreciated! Time is of the essence as I'm getting further and further behind each day this sits.

 

[DustyRusty]

Do you know the maintenance history on the machine? If not, I would be changing every filter on the machine, on the assumption that they haven't been changed in a long time. I had an Oliver tractor that would act up just like yours, and I would change the fuel filters, and it would clear up for 50 or 6o hours and then they needed changing again. I know that being an old tractor, that there was some sediment and rust in the tank, but there was no way to remove the tank for cleaning, without major disassembly. Filters were a lot less labor, so I lived with it.
I just went through a problem with my BX22, and changed filters, only to find that it was also a fuel pump issue. I could hear the pump running, but it wasn't pumping much. A new $20 fuel pump from Amazon saved the day.
My experience with Mercedes diesels has taught me that injectors rarely go bad, unless they get dirty fuel. After one injector problem, I started using diesel fuel conditioner, and never had a problem with injectors again.

 

[Land Warrior]

Do you know the maintenance history on the machine? If not, I would be changing every filter on the machine, on the assumption that they haven't been changed in a long time. I had an Oliver tractor that would act up just like yours, and I would change the fuel filters, and it would clear up for 50 or 6o hours and then they needed changing again. I know that being an old tractor, that there was some sediment and rust in the tank, but there was no way to remove the tank for cleaning, without major disassembly. Filters were a lot less labor, so I lived with it.
I just went through a problem with my BX22, and changed filters, only to find that it was also a fuel pump issue. I could hear the pump running, but it wasn't pumping much. A new $20 fuel pump from Amazon saved the day.
My experience with Mercedes diesels has taught me that injectors rarely go bad, unless they get dirty fuel. After one injector problem, I started using diesel fuel conditioner, and never had a problem with injectors again.

Thanks for your reply DustyRusty. The machine is serviced regularly and all the filters are also changed regularly. I hate to just buy parts until the issue goes away and would like a way to do testing to either eliminate or verify a problem component. The reason I added the fuel additive and changed the fuel filter is because it was the easiest to eliminate and because the machine was parked in a place where the sunlight hit it all day long warming it up possibly. With the warmer days and cooler nights we have been having here I thought some condensation may have formed in the fuel tank and then be causing the issue I'm having. Thanks again for your reply I will give the fuel pump a closer look.

 

[Russell King]

Has the temperature become much lower than when it ran well? The fuel may be gelling and not flowing well. Did the additives you used have anything for lower temperature? If you can get it into a warm place for several hours that would let you know if that is the problem. There are emergency additives that can help clear the problem but I live in Texas so know nothing about solving the cold problem other than wait for warm days.

 

[Henro]

White smoke may be telling you something.

I am no expert, by any means, but remember reading that white smoke is a sign of water...

Hopefully someone with more experience/knowledge can comment?

 

[Land Warrior]

Has the temperature become much lower than when it ran well? The fuel may be gelling and not flowing well. Did the additives you used have anything for lower temperature? If you can get it into a warm place for several hours that would let you know if that is the problem. There are emergency additives that can help clear the problem but I live in Texas so know nothing about solving the cold problem other than wait for warm days.

Actually it has gotten colder. I assumed the additive I put in the tank would take care of that also but I’ll have to read the label agin to be sure. Thanks I’ll check and be sure and if not I’ll get some that stop diesel From gelling.
thanks for the reply!

 

[whitetiger]

I am having issues with a Kubota KX121-3 S Series Mini-Ex. (2200 hours) the machine was parked for 3 weeks and not started but was running great when I last shut it down. The next time it was started it started perfect and idled fine while it was warming up. Then as I started to drive it started bogging down and sounded like the engine was about o die. I let off the forward controls and the engine smoothed back out and seemed okay. I checked the fuel gauge and it was at 3/4 tank. I was starting down a hill so thought it may have been about out of fuel which is what it sounded like. I managed to baby it down off the hill to a lower area to do some work and it seemed to get better as the machine continued to warm up. However when I when to use the bucket it would almost die again. Actually any hydraulic commands would cause this including forward or reverse. It did this three or four more times and then it cleared up and ran perfect the rest of the time I used it that day Approximately 4 to 5 hours work time. The next day I went to use it again and this time it would not clear up and run no matter how long I let it warm up. I finally shut it down.

A couple days of sitting once again due to rain, I purchased a new OEM fuel filter from Kubota. Also purchased diesel fuel additive that was supposed to remove any water, slime or algae from tank and also was supposed to clean injectors etc. ($20 + per bottle.) I added the prescribed amount of additive to the fuel tank. I then removed the sediment bowl and cleaned it out. There was no water in the bowl at all, but had a tiny amount of what looked like dirt possibly in bottom of it. I then removed the air filter and inspected the (outer air filter) It had some dust in it that I was able to tap the filter and it seemed to knock it out and I stopped when no more dust fell out then replaced it and reassembled the filter canister.

I then tried to start the machine and the sputtering and bogging down started immediately. I decided to let it run for a longer period of time to let the fuel additive and cleaner have time to work through the fuel system but it never cleared up. The machine with no load and at idle or even with the throttle up to mid-way it made no difference. It will run perfect then suddenly start to miss, sputter, shake and then almost die, puffs of black/white smoke come from exhaust, then clear up run perfect. After a few seconds or at times even 2-3 minutes o running perfect it will again go through the sputter event again. Doing this over and over no matter if engine has warmed or not. So....What else can I possibly check and also if it's an injector pump is there a way for me to check this to be sure without special tools etc. before purchasing one.
Additional Info:
I can hear the fuel pump and it sounds consistent as far as the sound it makes it doesn't appear to slow down or speed up. Although I haven't taken any lines off to ensure this flow is steady. I also haven't blead the system simply because when I researched how to change the fuel filter it was only recommended that the fuel shut off to the fuel sediment bowl (a clear see through bowl with a red ring that floats when water is present) then to wipe down the area around the filter prior to removing the old filter, then to fill the new filter with clean fuel and reinstall filter. Next turn the sediment bowl shut off back on and to turn key switch on for a few seconds before trying to start the engine. This was the prescribed way I found to "Prime" the system after fuel filter change and sediment bowl clean out. I cannot find a procedure online for actually bleeding the fuel system.

I have also pulled the parts schematic for the fuel system for this machine up online and according to Kubota's drawings that I found the prints have print item numbers for replacement purchases etc. There is a total of two filters. (not counting the sediment bowl) One was actually a strainer that is at the fuel tank entry. I would actually call this a fuel strainer rather than a filter but okay whatever....Potato, potatah. The other is the actual metal screw on filter. It is like the oil filter but smaller and silver with Japanese writing on it. If there is another filter somewhere in this fuel system Kubota failed to show this in their documentation.

Any help figuring out what to purchase or do to repair is greatly appreciated! Time is of the essence as I'm getting further and further behind each day this sits.

Take hold of the fittings in the sediment bowl head and see if one of them is loose letting it suck air. If they are tight, remove the outlet hose from the electric lift pump, turn the key switch to RUN, and see if you are getting a good stream of fuel from it. You may have restriction in the supply hose from the tank to the water separator or something in the fuel tank plugging the draw tube.

 

[Batesconst.inc]

Did you happen to find the problem? I have the same unit, same hours with the same problem. I can run it for a few minutes or hours and all of a sudden it'll start bogging. To the point, it sometimes will shut down completely. Sometimes I can let it set and it won't do it again until several minutes or a few hours. Sometimes it does it immediately. I can replace the spin on fuel fitlter and it may run fine for 15 minutes or it may run fine for several hours, but it'll start doing it again. I'm thinking it's a clogged fuel pick up screen, but not sure. Any pointers would be huge. Thanks.

 

[Land Warrior]

Did you happen to find the problem? I have the same unit, same hours with the same problem. I can run it for a few minutes or hours and all of a sudden it'll start bogging. To the point, it sometimes will shut down completely. Sometimes I can let it set and it won't do it again until several minutes or a few hours. Sometimes it does it immediately. I can replace the spin on fuel fitlter and it may run fine for 15 minutes or it may run fine for several hours, but it'll start doing it again. I'm thinking it's a clogged fuel pick up screen, but not sure. Any pointers would be huge. Thanks.

Problem Solved! Had a blockage in the fuel tank itself. I had tried blowing out the fuel line coming from the tank before but it still had the problem, so I assumed it was another issue. After changing the fuel pump and that didn't fix it I ran a temporary fuel line straight to the the fuel separator from a 5 gallon tank. It ran perfect so even though it appeared to be getting sufficient fuel supply from tank when running it actually was starving for fuel. That's why it was cutting out then I let off the controls and it would recover and I would move the controls once more and it would start to sputter and die out. I knew then that the fuel line coming from the tank had some sort of stoppage so I removed the fuel cap and used compressed air to blow back into the tank. This finally cleared it and the problem hasn't returned.
Hope this helps someone out with their issue. Do the fuel tank by-pass straight to the fuel separator first and this will tell you if you have a fuel supply issue at least up to that point.