Bad news big repair

[metalbender]

Being a vehicle tech for many years, sometimes an overlay is the easiest method. In this case, a simple pushbutton switch wired through a suitable relay to the glow plugs seems to be the answer. The original plug wiring is there, snip and attach as necessary. Terminate the original. Alternately, a diode could be installed into the original wire to prevent feedback to the ecu while using the added circuit so the ecu doesn't get confused.

 

[k0ua]

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”?

Leave the sensors alone, For that matter leave the relays alone. Leave everything as it is. Now install your own 70 amp relay, whose one side of the coil goes to the ignition +12 volt buss, the other side of the coil goes to a momentary push button that goes to ground, With the ignition key on, press and hold the button for 15 seconds, release it, start engine, and post glow by pressing the button for about 10 seconds after the engine runs. release button. Obviously the contacts of the relay go to the battery and the glow plug buss. It doesn't get any simpler than this. Obviously remove and store the original leads going to the glow plug buss. You don't care what the ECU is doing, what the sensors are doing or even what the original relays are doing.

 

[k0ua]

I don't think the computer will know the difference. The wire on the glow plug is after the relay. The computer control ends at the relay.

Yupp...

 

[ArtMech]

There is a slim chance if a specific capacitor or transistor can be identified as the culprit it can be replaced by an electronics repair shop.

When I was working at the car dealer workshop, we had a man who could repair the ECUs or injection computers of old cars at low cost.

I'd look for such a guy nearby.

 

[MossRoad]

...

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

...

Even if Kubota does the work? Ouch. We had a lot of machines at the newspaper that had proprietary boards. If we bought them, and it didn't resolve the issue, or we fried them, no returns. If we called a service tech in, and they fried them, no charge.

Cheap alternative to get by until a resolution might be to point a blow dryer down the intake for 10 minutes.

 

[Williy]

You could always install a hose heater in the lower
radiator hose then you would have a nice warm
tractor should start right away.
OR
build a fire under to warm her up?

willy

 

[Hay Dude]

She sits outside quite often with spreader tractor. Gets pretty cold

 

[Hay Dude]

Leave the sensors alone, For that matter leave the relays alone. Leave everything as it is. Now install your own 70 amp relay, whose one side of the coil goes to the ignition +12 volt buss, the other side of the coil goes to a momentary push button that goes to ground, With the ignition key on, press and hold the button for 15 seconds, release it, start engine, and post glow by pressing the button for about 10 seconds after the engine runs. release button. Obviously the contacts of the relay go to the battery and the glow plug buss. It doesn't get any simpler than this. Obviously remove and store the original leads going to the glow plug buss. You don't care what the ECU is doing, what the sensors are doing or even what the original relays are doing.

Understood, but if you cut the wire going to the glow plugs and splice-in an alternate source like you suggest, doesn’t the ECU detect a fault and derate?
I discussed this very idea last year with an ex military equipment tech, and he thought the ECU would detect a fault and derate

 

[Jchonline]

When I was working at the car dealer workshop, we had a man who could repair the ECUs or injection computers of old cars at low cost.

I'd look for such a guy nearby.

Yes the older boards are easy with just transistors and capacitors. Once you get into Integrate Circuits it gets tricky fast.

 

[dodge man]

Maybe an easy way to check if the bypass wiring would work would be to disconnect the glow plug wires. That’s will let you know if the computer “sees” that or not.

 

[K5lwq]

Understood, but if you cut the wire going to the glow plugs and splice-in an alternate source like you suggest, doesn’t the ECU detect a fault and derate?
I discussed this very idea last year with an ex military equipment tech, and he thought the ECU would detect a fault and derate

How? It is just a power wire with no feed back.

 

[RickB]

Understood, but if you cut the wire going to the glow plugs and splice-in an alternate source like you suggest, doesn’t the ECU detect a fault and derate?
I discussed this very idea last year with an ex military equipment tech, and he thought the ECU would detect a fault and derate

See post #20.

 

[PILOON]

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?

Yep, easy, you are now the 'intelligent' timer. 15 secs sounds about right but if it wont fire up simply repeat.
LOL, I knew one guy that simply pinched 2 wires that he'd dangled under his dash.

Note that glow plugs draw high amps so a relay would be needed as most switches max out at 10 amps.
At worst a starter relay could be used and activated with a simple push switch.

Hey, I once wired my GMC diesel plow truck to bypass their pricy 'timer' box.
Ran it that way for 3 years.

 

[ArtMech]

Yes the older boards are easy with just transistors and capacitors. Once you get into Integrate Circuits it gets tricky fast.

No, I didn't write about capacitors and transistors. The guy we were hiring was fixing the boards with integrated circuits. He could even reprogram the car comps of electronic injection if necessary. We had to find a computer from another car, which he copied the program from and reinstalled it into the fixed one.

 

[5030]

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?

Did you get it resolved? If not, think I'd wire up a switch for them direct to the battery and energize them for a bit prior to starting. Too bad the dealer don't have a spare ECU to test with. Glad I don't have that issue.

I guess if the glo plugs aren't working, I think I'd disconnect the buss that runs between each and go back to the old school shot of ether in the air intake. It does work you realize. If you have working glo plugs (which you don't obviously) using either can do real bad things...and modern starting fluid has upper cylinder lubricant in it so no dry starts. Sounds like it time (this summer) to off it.

 

[4570Man]

My old Chevy 6.5 has a sensor on the glow plugs that doesn’t allow them to cycle unless the coolant temperature is cool enough. The problem is the old and tired engine doesn’t like to start ever without glow plugs. I ended up wiring a manual jump switch to the solenoid so they can still function as intended but I can activate them manually if needed.

 

[Hay Dude]

How? It is just a power wire with no feed back.

I think the same as it monitors the air temp sensor and the water temp sensor

 

[RickB]

In the 4 hours you've been debating with people trying to help you you could have found out if disconnecting the glow plug buss from its power supply caused the engine to derate.
I'll bet the sensors are all two wire sensors with power and returning signal. The glow plugs are a single connection= power in.
That's how a sensor signal failure CAN derate the engine but an open circuit between the glow plugs and their power supply will not.
I think I'm done here until there is some meaningful information forthcoming.