B21 Kubota Tractor only runs in Start position with starter spinning

sbaughman · Oct 22, 2013

Hello -
Has anyone heard of this? The motor runs, but only if I hold the key in the start position with the starter spinning. As soon as I let the key fall to run, the motor stops. Any ideas?

This is a Kubota B21

thanks,
Scott

Gary Fowler · Oct 22, 2013

I have never had that happen but it sounds like the fuel solenoid cut off it closing when you release the key. Could be a bad ignition switch or shorted wire to the cut off. Can you hear the solenoid kick in when you turn on the key?

sbaughman · Oct 22, 2013

Yup - you can hear it. It actually is getting progressively worse. It used to be that it would run at the "glow plug" position and not the run position. Now it won't even go back to the glow position without it shutting off.

banjodunn · Oct 22, 2013

G'day as Gary said a suspect ignition switch.

Jon

shelkol · Oct 22, 2013

It can also be the fuse that powers the fuel shutoff solenoid. Had that happen on my BX2200.
Sheldon

troutsqueezer · Oct 22, 2013

shelkol said:
It can also be the fuse that powers the fuel shutoff solenoid. Had that happen on my BX2200.
Sheldon

There is a 5A fuse between the switch and the fuel cutoff solenoid. That's probably it.

Gary Fowler · Oct 23, 2013

I don't think it is a fuse as the OP can hear it click when he turns the key and a blown fuse wouldn't let it work in any case. After seeing more info, I would bet that the ignition key is the culprit. Put in a new one and problem will likely be fixed. I don't know what a new Kubota switch would cost, but to avoid wiring problems with a generic switch, I would spring for an OEM switch. Outside storage might be the major cause of switch failure, but then the B21 model is several years old and could just be worn out.

David_Kb7uns · Oct 24, 2013

I would suspect a fuse or switch or keyswitch in the keystop/deadman circuit that is causing the keystop timer relay to fire. On most of Kubotas smaller tractors the relay has power input from the keyswitch circuit through the safety switches and also a direct feed from the battery. When power is removed from the key circuit by interrupting the key switch or the safety switch the keystop timer relay fires off and close for the specified time sending power to the solenoid pulling the fuel rail lever to stop position. There is usually a click you here after the tractor stops and that is the relay releasing the solenoid. I do not have a B series book to look at but that is how it is on the other ones I have.

David Kb7uns

troutsqueezer · Oct 24, 2013

B21 schematic, if it helps.

crazyal · Oct 24, 2013

Do you have a multimeter? If so I would pull the 5 amp fuse (1 in the wiring diagram) and measure for voltage coming from the switch. When the switch is in the on position you should have power on one side. If you don't then I would turn the switch to the start position and see if you get power at the fuse. Just remember, if you pull the fuse you'll only get power on one side. If you have power at the fuse then I would measure for voltage at the fuel solenoid. If you don't have power then find the correct terminal on the key switch and repeat the tests.

if you don't have a multimeter then I would remove the wire going to the 5 amp fuse from the key switch and connect it to the positive side of the battery. Then try to start the tractor. If it stays running in the on position then it's your key switch.