Burnt 2018 L4701

[lottabusch]

Helping a friend make a decision.
The unit was connected to a water pump via the PTO. The shaft broke and most likely caused the grass under the tractor to catch fire.

There were half empty fuel cans sitting within three feet of the unit that did not combust to give you an idea how quickly the fire came and went.

It shut down on its own before anyone realized that happened.
The dealer has the unit and has quoted $12k for new wiring harness,ECU, alternator, starter, and a host of smaller ticket items.
The dealer states the unit overheated causing an electrical short which back fed into the harness.

I the attached pics you can see some heat related wire damage but IMO not wide spread.

Before I get myself into a project that will outlive me I wanted to get some opinions from the experts here and possibly get someone to come to the wilmington NC area put another set of eyes on it.

Any advice would be appreciated.

 

[Hugo Habicht]

From a warranty point of view I can understand why the Kubota dealer wants to replace the whole wire harness; this probably only comes in one piece and is probably fairly time consuming to replace.

On your pictures I can only see damaged outer plastic slieving. On the wires inside I cannot see any damage to the insulation, but there are other parts where the inner wires are not visible and there must be damage due to the tractor not running any more.

If it would be my tractor I would remove the plastic slieving around the damaged area, inspect and repair any damaged wires and put slotted slieving around it. One obstacle here may be that CAN bus wires for example require a specific impedance (sometimes twisted pair) so repairing those has to be done a certain way.

 

[lottabusch]

Thanks! The dealer has yet to confirm whether or not the motor is seized. I won't take it on if the motor is damaged.
Is it possible the motor overheated causing the wiring damage and potentially sparking the fire ? If that were the case it would suggest there could be major internal engine issues not yet discovered. If the broken PTO shaft caused the grass to catch fire subsequently melting wires which caused the engine to shut down Im less concerned about engine damage.

Is my logic flawed ?

 

[Hugo Habicht]

I do not think an engine itself can get that hot to cause a fire, maybe parts of the exhaust system. Catalytic converters are known to have caused fires when cars were parked over dry grass. A Diesel particle filter can also get very hot when regenerating I believe.

The connector of the alternator looks melted. Is that mounted fairly low down? An electrical fault there can easily start a fire.

Also my (garden) tractor has a fusable link, it is basically a piece of wire that acts as a last resort in a bad short. In my case this fusable link is located on the frame at the underside. Molten material from that link falling onto dried grass is certainly a possibility for a fire to start.

You mentioned in you initial post that the PTO broke and that this caused the fire. How do you believe this happened? Did it hammer onto something causing sparks to fly?

 

[North Idaho Wolfman]

Your big expense that you can't get around is the ECU and the programing of the ECU.
You can't program it yourself.
So that will require the dealer to do that part of it.
The rest is parts swapping.
If that has a plastic tank radiator, I'd be changing that too.

 

[Hugo Habicht]

The question is: is the ECU really faulty?

ECU nowadays are required to be designed to take all kinds of abuse, and that includes shorted outputs, voltage on any wire and even reversed supply voltage, overvoltage etc etc. .

So maybe you can check you ECU in another tractor before embarking on spending a lot of money.

 

[lottabusch]

I do not think an engine itself can get that hot to cause a fire, maybe parts of the exhaust system. Catalytic converters are known to have caused fires when cars were parked over dry grass. A Diesel particle filter can also get very hot when regenerating I believe.

The connector of the alternator looks melted. Is that mounted fairly low down? An electrical fault there can easily start a fire.

Also my (garden) tractor has a fusable link, it is basically a piece of wire that acts as a last resort in a bad short. In my case this fusable link is located on the frame at the underside. Molten material from that link falling onto dried grass is certainly a possibility for a fire to start.

You mentioned in you initial post that the PTO broke and that this caused the fire. How do you believe this happened? Did it hammer onto something causing sparks to fly?

We believe the that when the shaft broke about 2ft from the PTO it spun violently the 2ft section eventually broke the u-joint at the PTO. Sparks were likely flying during that process.
The dealer believes it overheated under load and caused the wiring failure.
Its important for me to understand what actually happened so we can focus on the fix.

 

[lottabusch]

The question is: is the ECU really faulty?

ECU nowadays are required to be designed to take all kinds of abuse, and that includes shorted outputs, voltage on any wire and even reversed supply voltage, overvoltage etc etc. .

So maybe you can check you ECU in another tractor before embarking on spending a lot of money.

That is good information. If I can't locate another tractor can I take it somewhere and have it tested?

 

[lottabusch]

Your big expense that you can't get around is the ECU and the programing of the ECU.
You can't program it yourself.
So that will require the dealer to do that part of it.
The rest is parts swapping.
If that has a plastic tank radiator, I'd be changing that too.

Yes I will make that suggestion and thanks ! I do know they have seen the red in the temp guage before but shut it down immediately.

 

[Hugo Habicht]

We believe the that when the shaft broke about 2ft from the PTO it spun violently the 2ft section eventually broke the u-joint at the PTO. Sparks were likely flying during that process.
The dealer believes it overheated under load and caused the wiring failure.
Its important for me to understand what actually happened so we can focus on the fix.

Hmmm... typically each wire (or the power supply of such) is protected with a fuse rated for the wire diameter. This is to ensure a wire can never get hot. The alternator wire to the battery may not be fused though, you have to check your schematics. My (garden) tractor has a fuse for the alternator wire.

Maybe @North Idaho Wolfman has first hand experience with such thing, but I cannot believe an engine getting hot enough to ignite anything. I would imagine it would seize long before that. It also means that all coolant liquid in the engine has to evaporate or escape first.

Exhaust system, including manifold, is a different story though (see above).

 

[Hugo Habicht]

That is good information. If I can't locate another tractor can I take it somewhere and have it tested?

Your ECU fits 10 tractor models (see picture below), so you could test it in any of them. If a dealer (or the factory) can (or will) test them I really do not know.

 

[lottabusch]

Your ECU fits 10 tractor models (see picture below), so you could test it in any of them. If a dealer (or the factory) can (or will) test them I really do not know.

Good to know and thanks! Would moving it to another listed working tractor potentially harm the surrogate or the ECU itself ?

 

[Hugo Habicht]

Good to know and thanks! Would moving it to another listed working tractor potentially harm the surrogate or the ECU itself ?

No, I cannot see that happening. I designed electronics for automotive and you would not believe what type of protection of all inputs, outputs and supply is required by the car manufacturer. I would imagine a reputable Japanese tractor manufacturer has the same requirements. You can't have a fried ECU just because a technician shorted a cable by mistake.

But ask your dealer, they should know for sure.

 

[ken erickson]

Is it possible the motor overheated causing the wiring damage and potentially sparking the fire ?

Looking at the clogged radiator I would say it was possible the engine overheated, but not speculating on if that caused the wiring damage.

If the engine did overheat to the extend of melting wires would it have not lost power and stopped before the wiring got damaged.

What seems even stranger is if the engine overheated, and finally quit due to melted wiring or just being way too hot, what caused the pto shaft to break two foot from the pto? Coincidence that both happed at the same time?

I would be more inclined to believe that the broken pto shaft caused the fire and ended up shutting down the engine due to wiring fire damage.

 

[lottabusch]

Looking at the clogged radiator I would say it was possible the engine overheated, but not speculating on if that caused the wiring damage.

If the engine did overheat to the extend of melting wires would it have not lost power and stopped before the wiring got damaged.

What seems even stranger is if the engine overheated, and finally quit due to melted wiring or just being way too hot, what caused the pto shaft to break two foot from the pto? Coincidence that both happed at the same time?

I would be more inclined to believe that the broken pto shaft caused the fire and ended up shutting down the engine due to wiring fire damage.

The pto shaft extension came apart because the pump guy used the wrong size and grade bolt. My buddy watched him do it.

 

[MapleLeafFarmer]

zooming into pic #1 it looks like the grass under the tractor burned and in doing so took out some of the low laying wires and alt. on the LHS of the engine compartment. Hoping it took out the fuse block of the 40/50a fuses near the rad overflow bottle thats low to the ground on the LHS and would stop the engine.

Hoping it took out the fuse block that sits near the overflow bottle leading to the tractor shutting down with rad hoses intact etc... If this is the case hoping the ecu should still be OK and the engine shut down w/o damage.

closer inspection and some better pic's of ecu and rest of engine compartment will yield much better opinions and thoughts.

Can you get better pic's of the engine on all sides and under the dash area? would be very usefull. The pic's very limited for good guesses some wider ones that we can zoom into would help of engine compartment and underside of tractor and above/below dash.

my first guess is if I didn't have insurance I would take on trying to repair it but more pics of larger areas will sure help

 

[lottabusch]

zooming into pic #1 it looks like the grass under the tractor burned and in doing so took out some of the low laying wires and alt. on the RHS of the engine compartment. Hoping it took out the fuse block of the 40/50a fuses near the rad overflow bottle that will stop the engine.

Hoping it took out the fuse block that sits near the overflow bottle leading to the tractor shutting down with rad hoses intact etc... If this is the case hoping the ecu should still be OK and the engine shut down w/o damage.

closer inspection and some better pic's of ecu and rest of engine compartment will yield much better opinions and thoughts.

Can you get better pic's of the engine on all sides and under the dash area? would be very usefull.

We are going to pick it up from the dealer next week and will begin assessing with pics

 

[D2Cat]

The pto shaft extension came apart because the pump guy used the wrong size and grade bolt. My buddy watched him do it.

So the PTO shaft did not break, it got pulled apart? That shaft dancing around there uncontrolled at 540RPM... what does the back of the tractor and the attached shaft look like?

 

[lottabusch]

So the PTO shaft did not break, it got pulled apart? That shaft dancing around there uncontrolled at 540RPM... what does the back of the tractor and the attached shaft look like?

Remarkably the tractor faired pretty well. I think the bolt was undersized and bored out the hole until it came apart. I was too busy helping put out the 1/2 acre fire to really take a close look at it.

 

[D2Cat]

You mentioned the pump guy used the wrong bolt. What bolt are you referring to? Wouldn't the PTO shaft be attached to the tractor and locked on with the setup there? The other end was bolted to the pump? I'm unclear how the pump was attached to the tractor by this "too small" of a bolt.