Bad news big repair

[Hay Dude]

Purchased my M135X in warmer months almost 3 years ago (April 2019). Never thought to see if the glow plugs worked. They actually won’t work if it’s over 41*.
Last winter, I realized the glow plugs weren’t working. Ohmed out wires, looked at wiring for mice damage, water damage, bad grounds, etc. Ohmed out wiring. Thats when I learned the glow plug system in larger kubotas is more complex than I thought. All 4 glow plugs passed electrical testing.
The glow plugs have 2 sensors one for air temp, one for water temp. The ignition switch is also part of the circuit. Then there are 2 relays and a fuse. All of this is controlled by the ECU. Last winter, I replaced
Key switch
water temp sensor
air temp sensor
both relays
fuse

Still no glow plugs. With nothing left to replace or test, I succumbed to a very reputable Kubota dealer. They basically did all the same things I did and replaced one of the new sensors I had already placed.
Still nothing. They called Kubotas double secret probation hotline and Kubota thinks it’s the ECU.

ECU price $6000
ECU Not returnable and no guarantee it will fix glow plugs.

So I’m out of answers. Any thoughts on other possible avenues to pursue?

 

[GSVette]

Not a good answer- how about just continuing to run without glow plugs? Neither my 8.2l Detroit Diesel nor the Cummins BT-4 have them. Yes they are slow to start in the cold and sound like a clattering bucket of bolts until they warm up ( not to mention the clouds of smoke). But they do start and run fine (once they warm up)

 

[dodge man]

A used one or rigging up some kind of switch on your own.

 

[Hay Dude]

Not a good answer- how about just continuing to run without glow plugs? Neither my 8.2l Detroit Diesel nor the Cummins BT-4 have them. Yes they are slow to start in the cold and sound like a clattering bucket of bolts until they warm up ( not to mention the clouds of smoke). But they do start and run fine (once they warm up)

Thats what I’m doing now, but at 25* the Kubota 6.1L gets real angry.

 

[k0ua]

Forget about the ECU. Just manually wire up and manually control the Glow plugs. A simple SPST pushbutton switch on the dash to control the glow plug relay. YOU will now be the ECU. You have a brain. Use that brain to control the glow sequence by turning on the ignition key pressing the button for 15 seconds, start engine, and "post glow" if necessary for a few seconds while the engine is running. Release button. Done. Now wasn't that simple?

 

[Hay Dude]

A used one or rigging up some kind of switch on your own.

ECUs are really unique. Each tractor has its own depending on when it was built and features. Not to say if I found the same tractor built around the same time it couldn’t be possible, but nobody would sell a used ECU from a donor tractor, they would want to sell with engine since engine can’t run without.
I did look around for one, though.

 

[Hay Dude]

Forget about the ECU. Just manually wire up and manually control the Glow plugs. A simple SPST pushbutton switch on the dash to control the glow plug relay. YOU will now be the ECU. You have a brain. Use that brain to control the glow sequence by turning on the ignition key pressing the button for 15 seconds, start engine, and "post glow" if necessary for a few seconds while the engine is running. Release button. Done. Now wasn't that simple?

I don’t think it’s that simple, but yes, the thought crossed my mind. They make timer switches too, so you can’t accidentally leave them on.
The sensors must stay in place. We tried to bypass the sensors and if you bypass them, the engine runs de-rated.

 

[RickB]

Forget about the ECU. Just manually wire up and manually control the Glow plugs. A simple SPST pushbutton switch on the dash to control the glow plug relay. YOU will now be the ECU. You have a brain. Use that brain to control the glow sequence by turning on the ignition key pressing the button for 15 seconds, start engine, and "post glow" if necessary for a few seconds while the engine is running. Release button. Done. Now wasn't that simple?

Probably the best low cost option. It is absolutely that simple. Use adequate sized wire directly from the battery, a properly sized relay and a control circuit from the relay to the operator station. I'd use keyed power for the control circuit.

 

[dodge man]

I’m not surprised a used ecu would be hard to find. It’s easy for me to say rig up a glow plug switch but I’m sure it’s not that simple. 10 seconds is all it takes.

 

[Hay Dude]

Probably the best low cost option. It is absolutely that simple. Use adequate sized wire directly from the battery, a properly sized relay and a control circuit from the relay to the operator station. I'd use keyed power for the control circuit.

The ECU reads the air and water temp sensors and they are both part of the glow plug wiring circuit and it has been stated that if the relays are bypassed, the tractor derates itself.
So how do you bypass all that and “simply install a switch”?