Tractor Starts But Won't Move

[marksb2620]

Kubota B2620 HST
Warmed up for 45 minutes. Air temp 12 degrees.
Hydraulics functioning, backhoe , loader.
When stepping on the forward , reverse foot peddles , the tractor stalls quickly, but can recover when taking my foot off the peddle.
I researched this yesterday and thought I had found the answer as a seat safety switch issue.
I cannot se that there is such a switch on my tractor. Only two smallish buttons where the seat makes contact which don't seem to activate anything.
All levers are where they were when the tractor was used last, about 2 weeks ago.

Thank you!

 

[ericm979]

Does it stall like the fuel to the engine is cut like when you turn the switch off, or does it strain like it's being asked to move an immoveable object? If it's the latter the brakes might be stuck on.

 

[marksb2620]

If I barely ask it to go forward or reverse, it might move about a foot before stalling / cutout /shuts off / no strain.
It does this when the shifter is in neutral too.
The engine starts and runs fine , throttles up nicely as always.

 

[Thomas]

Kinda sounds like vacuum leak.

 

[marksb2620]

I don't know what a vacuum leak is as I'm a pretty good operator and I don't have any experience/knowledge in mechanical repair.
I guess that tomorrow I'll tent it up and put the space heater to it.
I'd like to resolve this before the next storm as the yard needs to be cleaned up from the last dribble of snow.

 

[PILOON]

Might be a frozen hydraulic line in the drive circuitry.
Heat might be a cure.

 

[marksb2620]

I'll report back tomorrow.

 

[CobyRupert]

Not sure about your model, but you can usually follow wires to a seat switch.
If in fact the tractor isn’t stalling the engine under load because something is “stuck”, it sounds like it’s turning itself off because it “thinks” there’s an unsafe interlock condition.
What are the normal interlocks? When would safety interlocks normally cut out tractor?
Does you tractor have a seat occupied switch and a seat in vertical position switch? Do these work in conjunction with PTO and/or Neutral switch?
Is PTO on or off? Your symptoms sure sound like it thinks no one is in the seat and trying to drive (pressing hydro pedal).

Here’s a similar thread with a diagram. https://www.tractorbynet.com/forums/kubota-owning-operating/271245-2920-wont-start.html

 

[RjCorazza]

The manual indicated that there is a seat safety switch. My L4060 will start with me out of the seat, but pushing the hst pedal will immediately stall the tractor.
Rather than type out the various tests I've attached the manual section for an hst

 

[CobyRupert]

Yes, but....typically can you stand up and drive machine without it cutting out? If not, it’s probably your seat switch not recognizing that you’re sitting. (I.e. seat switch works in conjunction with pedal neutral switch)
....or do the seat switch test in the manual where you turn on the PTO.....but stay SITTING DOWN when you turn PTO on. If the tractor shuts off, again, it’s the seat switch not recognizing that you’re sitting.