Bad news big repair

[ptsg]

But on the other tractor they serviced, the ECU knew the GPs were out and set a code.

While in both cases, the issue affects the glow plugs, it can be two different things.

On the MX125, the issue could be on the control side of the relays, which can throw codes. On your tractor, the issue could be on the power side of the relays and the ECU have no way of knowing what's going on that side.

Have you tried to actually measure the power with the ignition on, on the control side of the relays to see if the ECU is not indeed turning the relays on?

 

[LHF2019]

9 pages and I counted 3 heater and 1 garage option. You mentioned it is on a spreader. You can't/or isn't parked near any source of electrical plug in accessible with extension cord? I understand it may not already have a block heater but seems like for the costs your looking at I would be considering another alternative. If the concern is it's parked outside and won't heat enough to start easy, that is not an issue as I do it on the NY/PA line and it can get much colder.

 

[Hay Dude]

9 pages and I counted 3 heater and 1 garage option. You mentioned it is on a spreader. You can't/or isn't parked near any source of electrical plug in accessible with extension cord? I understand it may not already have a block heater but seems like for the costs your looking at I would be considering another alternative. If the concern is it's parked outside and won't heat enough to start easy, that is not an issue as I do it on the NY/PA line and it can get much colder.

It’s not on a spreader, it’s used to load a spreader which is pulled by a Magnum.
It is usually parked outside, with no access to electricity. A block heater is a great accessory, but of no use to me.
Sometimes there’s an abandoned barn I can park it in which can help, but I always have to make sure the hood is accessible to my jumper cables.
Maybe your tractor starts easier, all diesels are different in that way. Some start easier than others. This one struggles under 30*.

 

[Hay Dude]

There were a lot of posts here so I may have missed something you have already tested. If this is so then I apologize for being redundant. But maybe I didn't miss anything so here goes. Since the ECU cannot power the glowplugs directly it must power a relay. So the first thing to check is if this relay is getting power to the relay coil when the glowplugs are supposed to be energized. If the relay coil is not getting power then check the wires from the relay coil to the ECU. If the wires are OK then check for power right at the ECU. No power right at the ECU? Then maybe it's the ECU. If it is getting power to the relay coil then check power to the relay contacts. If no power to the relay contacts then find the problem in the wires coming from the battery that go to the relay. If there is power to the relay contacts but none coming out then the relay is bad. The relay contacts could be bad or the relay coil could be bad. Make all these checks relating to the relay at the relay. If there is power at the relay output then the problem must lie between the relay and the glowplugs.
If there is no power at the ECU where the wires from the relay go when the glowplugs should be energized then the problem is partly or wholly in the ECU. It is possible, though unlikely, that the ECU monitors the glowplugs even when they are not energized. To check this remove the wires from the glowplugs and run the tractor. If it runs the same as before then the best work around is to then leave the wires disconnected and wire in a relay and push button switch, as was mentioned previously. If the tractor does constantly monitor the glowplugs there is another work around, also involving a relay or two, that will energize the glowplugs while isolating the ECU during starting, but will restore the ECU back into the circuit once the glowplugs are de-energized. If need be I will draw up the fairly simple circuit and post it.
Eric

I tried most of what you described last year. A lot of other repairs and life has gone by since then. This year I checked all the basics, then gave it to a Kubota tech, who did spend some time on it, checking wires and verifying the sensors, key switch, relays and glow plugs themselves work. His conclusion was it is a defective ECU. This was the conclusion given after he went up the chain of command and talked to someone at Kubota.

 

[K5lwq]

If you do decide to make a manual glow plug system I would use one of the old Ford starter solenoids. You can pick those up easily at any parts house for around $10 to $20. I have used them for many projects over the years.

 

[Tinhack]

Both my Kubota and Ford have manual engagement of the heaters through the switches. How hard can it be? My Kubota switch turns to the left for heat. It returns to OFF when you let go. The Ford has an intermediate switch position to the right. I included a light on the dash for my Ford to remind me to turn the switch off preheat.

When it's cold (according to my own judgment), I use the preheat positions for about 8-10 seconds for the Kubota and about 5 seconds on the Ford*. If they don't start right away, I repeat. They both usually start on the first try.

Gosh, if that's too complicated spend the $6000 at the dealer.

*The Ford heats a dribble of fuel into the intake after the filters--It doesn't use individual cylinder glow plugs.

 

[JimRB]

I have a 2003 VW TDI. My engine computer said bad number 3 glow plug. Indeed the ohm meter reading was high on number three. How did the computer know which glow plug was bad and turn on the warning light? The glow plug harness has 4 wires. I assume one for each glow plug. Note that each wire is less than a tenth of an inch with insulation so not very heavy wire gauge. The wiring diagram lists them as 1.5mm. The supply to that module hidden inside the ECM box has a 6mm red wire feeding it, a positive and negative for the relay, and two small wires out that go to another ECM module that tell it if the glow plugs look good. That rambling led me to the conclusion if my glow plug relay buried inside the ECM went bad I would need to have 4 jumper wires not wired together on the glow plug harness or the ECM would toss a code for glow plugs not showing correct resistance. I suspect you could jerry rig something but it might be 4 relays added to the glow plug wiring harness so it does not read incorrect resistance readings from each individual glow plug. My picture of my VW wiring diagram. On the bottom is just ground to the block for the glow plugs. I would suspect your tractor is doing a similar thing. As others mentioned, I think the glow plugs are supposed to operate for 10 seconds before the engine starts and run for a short bit after the engine starts to help ignite that diesel mix until the cylinders and pistons warm up a bit from combustion heat. Apologize for Captain Obvious comments especially if you have a good wiring diagram for your tractor.

 

[K5lwq]

This is the only reference I could find for the ECU wiring and codes without buying a service manual. It is for a M108x but I doubt there is much difference. On this one it only shows output to the glow system and no fault codes for the glow system.

I bet the terminal number is the same on the ECU plug. The glow relay is labeled 37 on the terminal layout. Maybe this helps.

https://www.service-engine.com.ua/webroot/pdf/KUBOTA%20M108X%20V3800%20ENGINE.pdf

 

[ovrszd]

Notice I didn't say anything about bypassing sensors or relays. If it doesn't derate now why would it with an alternate power supply for the glow plugs? You did say they aren't getting powered now, did you not?
I know you want to find fault with everything I post and frankly I don't care.
It looks like you have 3 choices.
1. The status quo.
2. A $6K repair.
3. Spend $50- 100 bucks on some decent components and see if I might be correct.

edit: You could also probably install a coolant heater and get by with it.

Yep, don't bypass anything, simply add a power circuit to the glow plugs.

I use a coolant heater on my M9540 and if it's plugged in the glow plugs don't activate. Starts like you just shut it off. Assuming the tractor is parked near a power source.

 

[JimRB]

There is a manual for a m130x at Scribd. Pages 458 to 462 explain how it works on a 130. It suggests it might be simple to do a momentary button to supply relay control ground on picture 5 terminal 5. Maybe the 135 works the same.