Oil & Fuel Kubota BX1860

[Professor49]

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]

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

 

[Professor49]

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]

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]

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

 

[itsjustme]

Have you tried unscrewing the fuel cap a few turns?

 

[Professor49]

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]

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]

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]

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