2020 Kubota M6-141 initially observed low PTO speed, then engine died itself, now won't start.

[Kaptain]

I’m reaching out for advice regarding an issue with my 2020 Kubota M6-141. Here’s what happened:

• A little over a month ago (July 7, 2025 to be exact), I used my M6-141 tractor (which had been sitting unused and exposed to the sun for several months) to run a John Deere CX15 rotary cutter. After about 15–20 minutes of mowing, I noticed the tractor was lacking power, then I looked at the dashboard, the PTO speed was only about 400 rpm (both the tractor’s PTO and the cutter are rated for 540 rpm).
  
  
• Soon after, the power seemed getting even weaker, and the engine began to die, eventually shutting off by itself. When I tried restarting, it would run for less than a minute, and then the engine shut off again by itself. Then I re-cranked it up, it the engine ran for just a few seconds and then died again. Then on the third or maybe the fourth attempt to re-start, the engine would only crank but wouldn’t start.
  
  
• After several failed restart attempts, I noticed the battery indicator light was on, and further cranking became slow and sluggish. I see the engine oil pressure warning light is on (I initially mistook this for the hydraulic warning light, so I went to the local dealer, bought a 5-gallon pail of Kubota Super UDT-2, and topped off the hydraulic fluid). I showed the picture of my dashboard indicators. The dealer says the one yellow dash light not indicative of low hydraulic fluid but engine air restriction and suggested me to replace the engine air filters, so I bought a pair of air filters from the dealer and replaced them with new ones. The old filters appear to be just fine and clean to me, not dirty or dusty at all. After the hydraulic fluid top off, and replacing the air filters, I attempted to restart it, but the engine only cranked but did not start. I called the dealer back trying to seek help, left a message, but received no call back.
  
  
  
  
  
  
• Because of other tasks I had to take care of, I left the tractor in the field as-is there for several weeks.

Now, today, August 13, 2025, I attempted to revisit the problem. I brought a battery jump starter with me and tried to re-crank up the engine but observed the exact the same issue as I left there - engine cranks but no start.

ANy thoughts or suggestions would be very much appreciated!

 

[Russell King]

I assume you ran the engine out of fuel. It could be just an empty tank, but is more likely a clog in the fuel lines or filters.

Do you treat the fuel in the tractor tank to reduce the growth of biological matter?

I would start seeing if you have good fuel flow between the tank and the filter. Then onto the injection pump.

Does the tractor have a fuel pump (not the injection pump) that feeds fuel to the injection pump or is it gravity feed?

If the tractor is high pressure common rail injection, then I would NOT recommend that you work on it very much. Get a dealer involved.

 

[BBFarmer]

Do you treat the fuel in the tractor tank to reduce the growth of biological matter?

How often do you recommend doing this and what product do you prefer using?

 

[Russell King]

I treat my fuel with Stabil products but it is not for biological growth. I have not had any issues with biological growth, just rust in the inside of the tank.

 

[Kaptain]

I assume you ran the engine out of fuel. It could be just an empty tank, but is more likely a clog in the fuel lines or filters.

Do you treat the fuel in the tractor tank to reduce the growth of biological matter?

I would start seeing if you have good fuel flow between the tank and the filter. Then onto the injection pump.

Does the tractor have a fuel pump (not the injection pump) that feeds fuel to the injection pump or is it gravity feed?

If the tractor is high pressure common rail injection, then I would NOT recommend that you work on it very much. Get a dealer involved.

Thanks for sharing your insight.
I did not run out of fuel. Never a single time since I bought it over 2 years ago.
The fuel level is currently slightly above the mid-level—the same level when the engine died.
See the current dash display showing fuel level. I opened the fuel tank cap and verified the liquid level.

Fuel pump - yes, it has one, labeled "Transistor Fuel Pump, 12V, Unit No. B6982, U-Shin LTD."

I have no fuel coming out from the fuel separator bleed point (B) or inlet point (A) when these screws are loosened, although I can see and feel the pump vibrates when key is turned on (not turning further to crank)

as far as treat the fuel in the tractor tank to reduce the growth of biological matter, I never thought about that and not sure how to, I'll do some dig/google search.
Thanks again.

 

[Russell King]

I would take A completely off the separator and see if you can get fuel out of that line with the key turned to run position.

If you get flow there, then you might look at cleaning the separator housing. There may be some type of strainer or elbow that have a bug or grass plugging it up.

If you don’t get flow there, then put A back on. Move to the inlet side of that pump and remove the fuel line there and let it run into a clean bottle for a few seconds to see if it has good flow.

I am surprised that A does not leak since the separator is full.

 

[Kaptain]

I would take A completely off the separator and see if you can get fuel out of that line with the key turned to run position.

If you get flow there, then you might look at cleaning the separator housing. There may be some type of strainer or elbow that have a bug or grass plugging it up.

If you don’t get flow there, then put A back on. Move to the inlet side of that pump and remove the fuel line there and let it run into a clean bottle for a few seconds to see if it has good flow.

I am surprised that A does not leak since the separator is full.

Yes, absolutely tested with the screw "A" completely off, it looked dry when taken off—with the key on and the pump humming/vibrating, not a single drop of fuel comes out of the fuel line.


Thanks for your suggestion on the next step of testing, hopefully tomorrow or the next couple of days. The weather is very hot in Texas in mid-August; I need to wait for a good day/time when it's not too hot.

 

[whitetiger]

Look under the RH steps; you will see a water separator, which the fuel has to pass through it before it can get to the pump. See if it is clean with no obstructions.

In your picture, you have a cap on the bottom of the fuel lift pump labeled "C". If you unscrew the cap, you will find the pump inlet filter screen. It may need to be cleaned; no need to replace it unless it is damaged or rusted.

 

[Kaptain]

Look under the RH steps; you will see a water separator, which the fuel has to pass through it before it can get to the pump. See if it is clean with no obstructions.

In your picture, you have a cap on the bottom of the fuel lift pump labeled "C". If you unscrew the cap, you will find the pump inlet filter screen. It may need to be cleaned; no need to replace it unless it is damaged or rusted.

Very good/useful information for me!
Thank you for letting me know. I'll report back once I done that.