Kubota ZD 21 won't shut off

[bubbauzz]

I had my Kubota ZD 21 zero turn loaded onto my trailer this afternoon and I went to unload and park it in the barn, but it wouldn't cut off. I turned the key to the off position and then removed it completely, but it continued to run. I engaged the parking brake and reset the steering arms to the outer positions, re-inserted the key, released the parking brake and stood up. It still ran. I drove it to the shop that is approximately 200 yards away and it started to sputter as if it were running out of fuel. It ran this way for approximately 60 seconds, then died. I didn't try cranking it back up, for fear that it wouldn't cut back off.

Any clues on why it would do this, and how to fix it?

 

[Rustyiron]

I would guess that it is an electrical issue with either the key switch or the fuel solenoid (or wiring to). Until you get it fixed, you could probably "stall" the engine at an idle by either engaging the pto, pushing the direction levers quickly to "fast" or if all that won't kill it, engage the pto and get up off the seat (assuming the safety switch works). Usually there is an audible "klick" when you turn your key to the first (run) position, and another klick when you turn it off. Try this before you start it again to help with your diag. It might just be a loose wire or connection, take a look.

 

[toxic]

My zd21 has done that before, it was the fuel shutoff solenoid. Open the hood and on the right side of the engine it will be underneath the air filter. The solenoid opens and closes the fuel shut off. That's the loud click you hear when you turn the key on, the solenoid opening. With the engine running you can manually close the fuel shutoff by hand.

 

[junkyardwarrior]

The later ZD21's (and 18's, 28's) had a fuel cut off solenoid located on the engine, directly pushing against the fuel control rack of the injection pump. The earlier ones had a solenoid mounted on the top with 2 10mm bolts holding it on, and the rod part of the solenoid connected to the fuel shutoff lever. If you have the early one, you can actually manually shut the thing off by moving the lever by hand. The later ones, you can't do that with them. BUT...I know you have an earlier one. How do I know. Because it won't shut off. The early ones work backwards in that they apply 12v to the solenoid to turn the engine off. The later ones apply 12v to turn the engine ON, so when you turn the key off on the newer ones, juice is cut off and the engine dies because the spring in the pump forces the rack back.

On your earlier one. We know that it applies 12v to turn the engine off by pulling the solenoid in. You will want to test the solenoid for 12v within 10 seconds of turning the key off from the on position (engine doesn't have to be running). If you get a 12v signal to the white wire at the solenoid, then the wiring and OPC controller is good. No power-usually means something is haywire in the OPC circuit. Lot of times the controller goes south, sometimes it's just the connector or wiring. The original controller is NLA, superceded/replaced with a new part number which I have yet to see fail. I don't know what they changed with them but they seem to be much better than the originals.

 

[smokin1cat]

I am also fighting is issue. Did you ever figure it out? I bought a new solenoid that wasn't the case. Checked white wire running to shut off and when motor is running it barely has enough juice to it to make the test light visible. I'm stumped checked wires as much as I could without stripping down the whole harness.

 

[KYKub]

I don't have a Z but on my G series Kubota I've had the same issue. Bothered me at first, but then started just turning it off by killing fuel manually as suggested above. Might be a bigger deal if you are using it commercially, but to raise the hood and kill the engine once a week when I mow isn't a problem. Jeff

 

[Tractorrr]

You could kill it by placing your palm over the air intake.

 

[David_Kb7uns]

Much more simple to pull the keystop solenoid rod or the fuel lever on models with internal solenoid. Most of the smaller Kubota engines use an energized solenoid to stop the engine and no power is required to run. If the keystop system is not working check fuse and interlock switches. Also check fuse on the keystop timer relay system.

David

 

[Gator6x4]

The later ZD21's (and 18's, 28's) had a fuel cut off solenoid located on the engine, directly pushing against the fuel control rack of the injection pump. The earlier ones had a solenoid mounted on the top with 2 10mm bolts holding it on, and the rod part of the solenoid connected to the fuel shutoff lever. If you have the early one, you can actually manually shut the thing off by moving the lever by hand. The later ones, you can't do that with them. BUT...I know you have an earlier one. How do I know. Because it won't shut off. The early ones work backwards in that they apply 12v to the solenoid to turn the engine off. The later ones apply 12v to turn the engine ON, so when you turn the key off on the newer ones, juice is cut off and the engine dies because the spring in the pump forces the rack back.

On your earlier one. We know that it applies 12v to turn the engine off by pulling the solenoid in. You will want to test the solenoid for 12v within 10 seconds of turning the key off from the on position (engine doesn't have to be running). If you get a 12v signal to the white wire at the solenoid, then the wiring and OPC controller is good. No power-usually means something is haywire in the OPC circuit. Lot of times the controller goes south, sometimes it's just the connector or wiring. The original controller is NLA, superceded/replaced with a new part number which I have yet to see fail. I don't know what they changed with them but they seem to be much better than the originals.

Very good. A good description on how the system works along with how to Check and diagnosis the problem and the probable cause of the problem experienced.

 

[lakeside]

This may or may not help. at about 200 hours my G1800 wouldn't stop so I'd have to manually pull on the fuel shutoff, really doing the same thing as the solenoid but by hand. I bought a generic manual fuel shutoff cable, disconnected the solenoid, installed the kit and connected the manual shut off. I now turn the key to the off position and manually pull the black plastic knob. Being doing that for on to 12 years now and it works fine.