Bad news big repair

[LittleBill21]

there is a wiring diagram above, according to that diagram it should be a ground, not a 12v line. grounding it should cause the gp to come on regardless of the ecu is trying to do.

 

[bearthebruce]

there is a wiring diagram above, according to that diagram it should be a ground, not a 12v line.

Yep - missed the link in post #88. Sorry. Ground it is.. pin 37 of the ECU has to go to ground to turn on the relay.

The only temp sensor I saw was the engine cooling temp sensor. To spray the freeze spray, you would have to remove it from the radiator which means the hole in the radiator has to be plugged so all the coolant does not come out. I don't think that is gonna git er dun..

I'm not sure how to fool the coolant temp sensor into thinking the ambient is glow plug worthy... I'll think on that.

 

[Alan46]

302 posts and counting. It just shows how good this site is!

 

[WranglerX]

Well heck here goes;
View attachment 725057
Terminal layouts

The automotive ISO mini relays above are typically available in two types of pin layout designated Type A and Type B layouts. These layouts are shown on the two 5-pin relays below (pin 87a not present on 4 pin relays):

Terminal/Pin number	Connection
85	Coil
86	Coil
87	Normally Open (NO)
87a	Normally Closed (NC) - not present on 4 pin relays
30	Common connection to NO & NC terminals

Per what has been posted here it is a possibility that your ECM is providing the ground for the relay coil either T85 or T87.
One way to verify that would be a voltage check of the relay base with the key turned on check for voltage on T85 or T87 of the relay socket,
if you have voltage on either of those then the ECM is providing the ground for the coil.
While the relay is removed you can look for voltage on T30, T87 or (T87A not likely) if so the system is good to the relay.

Also you could disconnect the battery and using an ohm meter check from the relay(s) from T87 to the glow plugs for continuity,
it may be T30 but normally that would be battery power but I have seem T87 used for power and T30 to the powered device.

If your system does not have the ECM grounding the relay coil with one side of the relay coil having voltage present whenever the key is on,
then one of those terminal T85 or T86 should be going to ground.

This link has a lot of good information on relays;
Automotive Relay Guide | 12 Volt Planet

Have fun.

Suggest you check you use of "T87" in your text.... Don't you really mean "T86"...

 

[RickB]

Yep - missed the link in post #88. Sorry. Ground it is.. pin 37 of the ECU has to go to ground to turn on the relay.

The only temp sensor I saw was the engine cooling temp sensor. To spray the freeze spray, you would have to remove it from the radiator which means the hole in the radiator has to be plugged so all the coolant does not come out. I don't think that is gonna git er dun..

I'm not sure how to fool the coolant temp sensor into thinking the ambient is glow plug worthy... I'll think on that.

A judiciously placed resistor of the proper value.

 

[LouNY]

Suggest you check you use of "T87" in your text.... Don't you really mean "T86"...

Yes good catch,
I went back and edited it.
Thanks for catching it.

 

[LouNY]

On some tractors disconnecting the temperature sensor will put the intake heater into default which is the longest time,
some will also have two temperature sensors also one for indication and one for manifold heat.

 

[dpgood1]

Do you have full coverage? The tractor could catch fire "accidently".

 

[bearthebruce]

Would Hay Dude have a resistor laying around? I know I have lots of them.. because earlier in my life I made a living as a sparky... But Hay Dude admits its been awhile since he did electrical/electronic stuff.

Here is a typical temp sensor spec:
Coolant Temperature Sensor; Outline Of Coolant Temperature Sensor; Structure Of Coolant Temperature Sensor; Function Of Coolant Temperature Sensor - Kubota D1803-CR-E4 Workshop Manual [Page 133] | ManualsLib

You'll see that the coldest temps produce high resistance. To fake it, unplug the coolant temp sensor and the glow plug circuit ought to be active. Unplugged = the equivalent of -40C or some crazy value.

That should let you at least check that the relay is being pulled in.

 

[RickB]

Would Hay Dude have a resistor laying around? I know I have lots of them.. because earlier in my life I made a living as a sparky... But Hay Dude admits its been awhile since he did electrical/electronic stuff.

Here is a typical temp sensor spec:
Coolant Temperature Sensor; Outline Of Coolant Temperature Sensor; Structure Of Coolant Temperature Sensor; Function Of Coolant Temperature Sensor - Kubota D1803-CR-E4 Workshop Manual [Page 133] | ManualsLib

You'll see that the coldest temps produce high resistance. To fake it, unplug the coolant temp sensor and the glow plug circuit ought to be active. Unplugged = the equivalent of -40C or some crazy value.

That should let you at least check that the relay is being pulled in.

More likely to throw an open circuit fault code.

 

[bearthebruce]

Then put a 3k resistor in place. If ya have one.

 

[Henro]

@Henro
Agree in general, but if that’s your accusation, could you find anywhere where I rejected anyone’s reasonable suggestions?
Heres my post on Saturday when the tread was started:

I don't think I was pointing that comment at anyone in particular.

Sorry if you took it that way...not my intention.

 

[etpm]

Yeah thats true.
I will add it to the list of possibilities
Going to try to see if corrosion of the ECU and plug fixes it first. If it doesn’t, will pursue on board DIY glow plug set up or maybe a generator to power a block heater.
I really should buy a small portable generator one of these days….

I don't know how you plan to take care of the corrosion but I do have a suggestion. I use some stuff called Deoxit. It comes in several formulations. I use the D5 stuff on the connectors in my CNC machines. The stuff actually works and all sorts of electronics repair folks use it and have done so for years. It has a very good reputation. It is made by Caig Labratories, according to my can.
Eric

 

[etpm]

That .58 volt reading should be considered spurious. Because modern digital meters put almost no load on the circuit being tested because putting a load on a circuit will cause a voltage drop. This means a voltage could be present from just plain leakage through dirt and humidity. Dust on surfaces can conduct electricity if there is enough moisture in the dust from ambient humidity. It will not conduct well, the resistance will be sky high. The resistance in your digital meter is also sky high. So even though some voltage will pass there will be no current to speak of. Anyway, when you see voltages like that .58 volts in an automotive type circuit that is controlling a relay you can pretty much discount it as anything important.

 

[5030]

I believe in supporting my local dealer but I have to draw a line somewhere. I'm sure he didn't pay that much for it and the one I removed wasn't even labelled Kubota. Was labelled Nippon Denso. So was the replacement.

 

[Hay Dude]

For the heck of it, I tried a jumper wire for 10 seconds and the tractor started like a champ.
I guess it’s pretty close to “wire up a switch“ time.
Yeah, I know like 30 people suggested it and it always was my “end game” if I couldn’t fix the OEM system (without spending 6k replacing ECU).

I‘m still convinced something else could be wrong other than the ECU, but there’s only so much time I can steal from working in the fields. It needs to be worked on when it’s cold to get the GPS to work and that gets old pretty fast.
I appreciate all the suggestions and the effort by some. Even with the few trolling, it was worth it.

 

[Hay Dude]

I believe in supporting my local dealer but I have to draw a line somewhere. I'm sure he didn't pay that much for it and the one I removed wasn't even labelled Kubota. Was labelled Nippon Denso. So was the replacement.

Denso is one of the biggest automobile assembly producers in the world. Electronics is their wheelhouse.

 

[5030]

Hell, I didn't care if the relay said Joe Blow on it, so long as it worked...and it did.

 

[ptsg]

For the heck of it, I tried a jumper wire for 10 seconds and the tractor started like a champ.
I guess it’s pretty close to “wire up a switch“ time.
Yeah, I know like 30 people suggested it and it always was my “end game” if I couldn’t fix the OEM system (without replacing ECU).

I‘m still convinced something else could be wrong other than the ECU, but there’s only so much time I can steal from working in the fields. It needs to be worked on when it’s cold to get the GPS to work and that gets old pretty fast.
I appreciate all the suggestions and the effort by some. Even with all the trolling, it was worth it.

On your first post, you mentioned that you replaced both water and air sensors. If you still have the "old" sensors around, you could plug those up and put them on a cup of cold water/ice to trick the ECU thinking it's cold weather. This would be helpful for the troubleshooting process.

 

[Hay Dude]

On your first post, you mentioned that you replaced both water and air sensors. If you still have the "old" sensors around, you could plug those up and put them on a cup of cold water/ice to trick the ECU thinking it's cold weather. This would be helpful for the troubleshooting process.

That’s a great idea. I did save them. I just don’t have the time as these tractors are badly needed for work. I don’t know if it’s worth falling behind much further to mess with it.