TLB48 Throttle run away

[Firemedic]

I have a 2006? TLB 48 with approx 225 hours on it.
Today I was digging stumps for approx an hour and shut the machine down to go get a shovel. The machine has been running fine. My buddy went to drive the tractor up to the house, he was driving, approx 75 yards up a slight incline, when the motor reved up like something I have never heard. It sounded like it was surely going to blow up. He tried shutting it down but the key did not turn it off, he jumped out and the dead man switch on the seat did not shut it down either. It was running way faster than it would with the throttle set open, which he had not moved. We cut the fuel line coming from the pump to get it to shut down.
We let it sit and fixed the fuel line. After getting the air out of the line it started up and is now running fine. The oil appears to be ok and not full of fuel.
I'm out of ideas as to what could have caused this??? I'm not sure what to check/repair to keep this from happening again.
The dealer suggested:
solenoid that cuts the fuel to the motor when key is turned off, but why would this dump excess fuel in the motor??
Low battery voltage.. My battery seems fine
Faulty fuel pump causing excess fuel to be sent into the crankcase.

Any help is appreciated

Thanks

Mike

 

[Theekillerbee]

Sounds crazy! I draw a blank on that one...I don't think that motor has any kind of governor that could fail and cause the problem. I'm not familiar with the electronics on the newer tractors, so I hope Vic, OB1, Eserv, or any others with knowledge of your tractor chimes in.

 

[Ob1kubota]

Firemetic welcome aboard and this is a very interesting problem. I call it diesel run away and you are quite right it will run until the lube oil can't keep up with rpm or the overspeeding bends a valve train component or worse throws a rod through the block. A diesel is like the fire triangle you have to shut the air off, cut the fuel or reduce the speed below auto ignition for comparison. To reinforce what Antietam Tractor told you next time ( if it ever happens again ) don't panic, simply open the hood in a workman like manner and locate the RED painted screw on the HP injection pump fuel inlet housing and simply close it against the throttle stop effectively shutting the fuel off. If it doesn't stop, while still holding the valve shut remove the air cleaner cover and filter element and plug the air inlet tube with a cloth restricting air intake. This will kill it. I'd have Antietam Tractor run some fuel system checks and submit a technical information request to Kubota Service Engineering on Kubotalink before I'd treat myself to another uncontrollable overspeed event.

 

[eserv]

I asked about this problem here also and no one had ever experienced it except in cold weather where moisture in the engine oil caused the fuel rack to freeze up This only happened on a cold start. Obviously the fuel rack was stuck on yours if it wasn't caused by an external fuel supply. But I don't know what caused it. The fuel rack on our Deutz engines in the Gehl loaders sometimes stick and Gehl recommend that we put ATF in the fuel periodically to prevent it, you could try the same thing.
Ed

 

[aquaforce]

I Hope a good solution is found for this situation.


In my career I have had one runaway on a 6cyl Ford engine. The turbo shaft broke pumping engine oil into the intake, so of course I couldn't get it shut down because the air piping was to secure to get off before the entire building ( somewhere in the ball park of 65 to 75K square foot) full of smoke and it poured out the overhead doors (21) like the whole thing was on fire. WOW!!! The engine shut off when the oil was all gone. Scarry. No harm to anything but a huge mess out the tail pipe too.


Good luck with this.