Kubota excavator bogs under load, HELP

[John123!]

2019 kubota U35 1200hrs

Machine bogs under load (digging/picking things up w thumb)

Bought machine used. Put 10gals road diesel in it on the way home. Went to use it a few days later and noticed it would bog down while picking up some brush.

I've replaced fuel separator filter and cleaned housing. Replaced fuel filter and cleaned housing. Blew out lines. Blown line back towards tank. Drained a cup of fluid from the tank drain.

I have steady stream leaving fuel filter and going to injection pump.

At this point I'm out of ideas and kind of stumped. Going to measure the Temps on the exh. manifold and take machine to kubota for them to hook it up to their ACE (whatever that is) tester.

Any suggestions are appreciated. I have some videos I will try to post also.

 

[Simon C]

Have you tried to pinch off the fuel return line to see if it runs stronger. Some return check valves have been known to fail.
Simon C

 

[materthegreater]

What does the air filter look like?

 

[MG84]

Have you tried to pinch off the fuel return line to see if it runs stronger. Some return check valves have been known to fail.
Simon C

On the same note, make sure the fuel return line going back to the tank isn't plugged. The entire system needs to be free/clear to flow the way it is intended to or you can get fuel starvation issues. Also make sure that the fuel tank is venting properly, try running it with the cap off.

It is also possible its a problem with the injection pump itself. I have a 2022 Kubota L2501 tractor that had similar symptoms (bogging under load/stuttering/not achieving full throttle and it was intermittent), ended up being a defective injection pump. Replaced under warranty, works great now.

Also, FYI, the machine uses a completely mechanical injection engine. There is little to no computer diagnostics the machine is capable of regarding the engine. Just have to figure it out the old fashioned way.

 

[John123!]

Filters are all new.

Took it to the dealer, they said it was over serviced 2 gals of hydraulic fluid and the filter vent was clogged/wet. Seems to have power back, I haven't had chance to run it much so time will tell.

2 days @ dealer. $235

 

[MG84]

Interesting, that's one I haven't come across yet. Let us know if that did indeed fix the problem.

 

[John123!]

Kubota dealers "fix" did not fix the issue. I knew better.

Still bogging/lack of power under hydraulic load.

I would like to check the fuel pressure of the lift pump but don't know what it should be.

After that, maybe pull the injectors and send them out to be tested?

Any ideas are appreciated thanks.

 

[John123!]

Have you tried to pinch off the fuel return line to see if it runs stronger. Some return check valves have been known to fail.
Simon C

I like that, I'll try that!

 

[John123!]

What does the air filter look like?

New kubota air filters. But thanks for the idea!

 

[John123!]

On the same note, make sure the fuel return line going back to the tank isn't plugged. The entire system needs to be free/clear to flow the way it is intended to or you can get fuel starvation issues. Also make sure that the fuel tank is venting properly, try running it with the cap off.

It is also possible its a problem with the injection pump itself. I have a 2022 Kubota L2501 tractor that had similar symptoms (bogging under load/stuttering/not achieving full throttle and it was intermittent), ended up being a defective injection pump. Replaced under warranty, works great now.

Also, FYI, the machine uses a completely mechanical injection engine. There is little to no computer diagnostics the machine is capable of regarding the engine. Just have to figure it out the old fashioned way.

I might try to pinch off the return line and see how it performs.

How can I test the injection pump without removing and sending it off etc?

 

[Gary Layton]

I posted this in another thread also...

You should look at fuel starvation, I think. I have a CAT 320CL, 2006...bought it 2 years ago. It ran strong until I had recent service done (head gaskets replaced and hydraulic PRV things fixed). I got it home and it ran great for about an hour then started bogging down under any load.


CAT/Yancey took it back to the shop and found this...it was tank gunk...rust, algae, whatever. They removed the fuel tank, pressure washed it, cleaned out fuel lines, changed filters, etc. Now it runs great.

Check your fuel system.

 

[ravenranch]

Did you find out the issue regarding your bogging down? I have a kx033 kubota that is doing same thing. only 600 hrs. changed all filters, fuel and hydraulic suction/return air filters. When tracking it boggs down. Under any heavy load it boggs down. Stumped.

 

[ps66x4]

Every time I had that happen something was plugged up.

 

[heymccall]

Just search "3972" on here under compact track loaders.

The water separator inlet elbow is probably debris restricted.

 

[ravenranch]

Just search "3972" on here under compact track loaders.

The water separator inlet elbow is probably debris restricted.

yeah mine is not. already checked that. clean as a whistle

 

[ravenranch]

For anybody that experiences a bog down event and changes all filters and still has issues

Mine was resolved by turning the fuel adjustment screw by the fuel shut off valve out 1 turn.

Been chasing this issue for a year

Kx033 running like new now