Oil & Fuel Kubota BX1860

Professor49 · Jun 4, 2015

Hi there! I'm new here, so bear with me.

I have a Kubota BX1860 diesel tractor about 3-years old. During the Spring and Summer it gets used weekly for mowing with a 54" belly mower. This year during my third 4-hour mowing session the engine started bogging down, rpms dropping rapidly and rough running as though it was not getting enough fuel. I disengaged the mower deck and idled the throttle. The engine ran roughly for a few seconds and then began to gain rpm again so I throttled up to mowing rpm and continued. After about 15 minutes the same thing happened again. After that this repeated at shorter and shorter intervals each time. On the way back to the shop with the mower deck disengaged the engine had the same problem while traveling up hills where the load increased on it.

I picked up some new fuel filters and replaced both upper and lower and when I mowed next I had very heavy, tall grass overgrown due to lots of rain and no chance to mow. I mowed this very heavy load for 90 minutes with no problem and then the problem returned. This time I stopped and cleaned the mower deck and did not get back to try more mowing for about half an hour. When I did I start it back up I mowed some normal lawn grass for 45 minutes before the problem returned.

I changed the lower fuel filter a second time but it did not seem to have gathered any debris and the problem continued when I used the tractor more just driving around the property without mowing anything. Any ideas I can try before calling the Kubota dealer to come pick it up and take back to a mechanic?

JOHNTHOMAS · Jun 4, 2015

I would check all wiring connections to ensure one isn't loose and moving with vibration.:2cents:

Professor49 · Jun 4, 2015

Thanks for the advice, but I've already checked all wiring that I could access looking for loose connections or rodent chewing activity but found nothing amiss.

I wonder if anyone knows what the fuel pressure should be from the fuel pump and if it could be checked by pressure. The fuel flow seems low to me even when running OK, but I don't really know what is normal.

Baby Grand · Jun 4, 2015

JOHNTHOMAS said:
I would check all wiring connections to ensure one isn't loose and moving with vibration.:2cents:

Along these lines, check that the operator presence (seat switch) isn't opening when you shift your weight in the seat. Also check that the PTO switch isn't opening.

How has the temperature gage been looking during all of this? Oil level okay?

There have been a few posts in the past where an object floating in the fuel tank will periodically get sucked into the port that is connected to the fuel line, blocking it. The object gets sucked there and held in position until the engine slows down or stops and the pump stops creating suction. Then it moves away until the engine runs again for a time and it gets sucked back over the port.

SeymourBota · Jun 4, 2015

Something is floating around in the fuel tank and randomly blocking the fuel pickup at the bottom of the tank.

itsjustme · Jun 4, 2015

Have you tried unscrewing the fuel cap a few turns?

Professor49 · Jun 5, 2015

Thanks for all of the suggestions.
1. Seat switch - seems to be working OK since it kills the engine immediately while PTO is engaged if I lift my weight from it. No sputtering, rough running but immediate kill instead.
2. PTO switch - ditto. It kills the engine immediately if I am not in the seat and try to engage it.
3. I cannot figure out any manner of inspecting the fuel tank without removing it and I can't figure out how to remove it. This will need to be checked by the dealership mechanic when I give up on all other things that I am capable of doing with my limited mechanical abilities.

Professor49 · Jun 5, 2015

This is a possibility I suppose, but I don't know how to check this myself. I am very careful with fueling and find it very hard to believe that anything would have gotten into the tank accidentally while fueling. Never say never - nothing is impossible. It doesn't seem to fit the time related issue since the problem occurs more frequently the longer I run the engine and has not yet ever occurred within the first hour of operation.

Professor49 · Jun 5, 2015

I have tried loosening the fuel cap - nothing changed. I also cleaned the fuel cap vents - I can see how a lot of dust can enter through those as dirty as they get. I have had this problem with other equipment over the years so this was the first thing I thought of and tried. Thanks for the suggestion, though. It is a good one - plugged fuel cap vents have has caught me off guard more than once.

RalphVa · Jun 5, 2015

I had something similar happen on my JD 4010 (18 hp diesel).

Some wax had come out of solution during cold nights in the winter. The wax globs were partly plugging the fuel tank outlet line.

I had to siphon off the fuel and then get a retrieval tool (a mechanic's tool with 3 little fingers on the end, actuated by a button on the end of the cable) to fish out the wax globs. Some warm kerosene would likely have dissolved it, if I wanted to go that route, but heating the kerosene can be dicey.

Ralph

shadowshack · Jun 6, 2015

I had similar issues with my BX25. I was ready to bet the farm I don't have that it was fuel related. Changed the filters as you did, with no improvement. Finally gave up and let the dealer take it when I needed it most (dead of winter with snow after snow piling up in my driveway). They said the parking brake wouldn't fully disengage and it continually put a load on the engine. As I would use it more, the engine would bog down even more. Once I got it back the problem never reoccured. Go figure.

Professor49 · Jun 7, 2015

Thanks for the information. I will check this out, but I haven't seen any indication that this might be the case.

shadowshack said:
I had similar issues with my BX25. I was ready to bet the farm I don't have that it was fuel related. Changed the filters as you did, with no improvement. Finally gave up and let the dealer take it when I needed it most (dead of winter with snow after snow piling up in my driveway). They said the parking brake wouldn't fully disengage and it continually put a load on the engine. As I would use it more, the engine would bog down even more. Once I got it back the problem never reoccured. Go figure.

anthonyv · Jun 7, 2015

Have you checked to see if the fuel sender is not rusting out & the rust particles are plugging the tank outlet? There have been several posts regarding this same issue.

Professor49 · Jun 9, 2015

I'm a dummy here...not sure what the "fuel sender" is... The tractor is only a couple of years old.

anthonyv said:
Have you checked to see if the fuel sender is not rusting out & the rust particles are plugging the tank outlet? There have been several posts regarding this same issue.

JOHNTHOMAS · Jun 10, 2015

Several of "us" have dropped stuff in the fuel tank over the years. Usually a cap, lid, spout, ring or something from our fuel can. Some threads in the past. The best method to retrieve the "stuff" is to turn the tractor upside down and shake it till the item comes out

but most of us aren't that strong. Or lay it on its side and maybe it'll roll out.

I did finally get my part out (I think mine was the pour spout) by letting my wife have a go at it with a full tank of fuel which made it float near the top where she could see it but I never could. It never hindered the running of my tractor but just knowing it was there bothered me.

anthonyv · Jun 10, 2015

Sorry I meant the fuel gauge sender switch under the fender on the left side. A float is mounted on a steel wire then to a switch inside the fuel tank & controls the fuel gauge display. There have been several complaints & many previous posts about this wire & the switch housing rusting & plugging the fuel outlet & filters. If this is what is occurring the only option is removing the fender & replacing the fuel gauge sender unit & cleaning the particles from the tank. Here is one thread that may help. http://www.tractorbynet.com/forums/kubota-owning-operating/222371-rough-running-bx.html

dodge man · Jun 10, 2015

Next time this happens, take the fuel line off after the back filter. If the flow of fuel is very low or almost none, then the filter is plugging up or the tank is plugging up. If the flow is low, then take if off before the filter and if the flow is good, then its the filter for sure. Mine plugged up about once a year. There are some threads on here about putting a Racor filter on the BX, this usually solves the problem of the filter plugging up. The factory filters are very small and plug very easy. Of course the problem with all my advice is that the mower deck is in the way and you probably have to pull it to get at the rear filter.

Professor49 · Jun 24, 2015

Thanks for the advice. Since I last posted I have definitely figured out that something was lodged in the fuel line between the tank and the filter. I purged back into the tank with slight air pressure after loosening the fuel tank cap and could feel the line pressuring up before the restriction broke loose and I was rewarded with a full stream of diesel in my face where there had only been a dribble before. The feel of the pressuring made me feel pretty certain that the restriction was something soft in the line and not in the tank at the inlet since it seemed stuck. Hard to explain, but I'm convinced of this. Problem is now that whatever it was is in the tank now and I still don't know how to get it out. I guess I'll just proceed as normal until the problem returns. I've put quite a few hard hours on the tractor since I blew the line out and there has been no recurrence of the problem yet. Some people spoke of algae problems - something I've never experienced in my 15 years of owning and using Kubota tractors ( all 3 fueled from the same supply tank), but anything is possible. Thanks again for everyone's advice. I guess I'll just see if the problem returns or not...any maybe treat the diesel to prevent algae even though I've never seen any.

dodge man said:
Next time this happens, take the fuel line off after the back filter. If the flow of fuel is very low or almost none, then the filter is plugging up or the tank is plugging up. If the flow is low, then take if off before the filter and if the flow is good, then its the filter for sure. Mine plugged up about once a year. There are some threads on here about putting a Racor filter on the BX, this usually solves the problem of the filter plugging up. The factory filters are very small and plug very easy. Of course the problem with all my advice is that the mower deck is in the way and you probably have to pull it to get at the rear filter.