Kubota G1800 won't shut off

[goodolboydws]

It sounds as if you're headed down the road of replacing the controller box for no reason other than to stop the diesel pump from running momentarily. Depending on your inclination, mechanical and electrical ability, or financial wherewithal, there are several viable choices-some already posted.

1. put in a battery post-type mount power disconnect switch (quickest, simplest, and cheapest solution)

2. As someone else has already stated, you could simply wire in a battery power cut off switch. (dash mounted or easily accessible from there would be nice)

3. Keep checking eBay for a used one. Use a Want-It-Now posting if one isn't there in a week or 2.

4. Cut open the old box. If so, using a Dremel type tool often works with the least physical damage to the case. I've even opened up individually epoxy-potted relays this way TO CLEAN, BURNISH, OR BE SURE THAT THE INTERNAL CONTACTS ARE IN GOOD SHAPE and resealed them with epoxy afterwards.

Just for curiosity, before opening up a possible good part, You mentioned that this tractor is about 20 years old. Many times the electrical contacts in connectors as well as in relays can get crudded up to the point that whatever depends upon their proper functuioning will slowly get worse and worse over time. Did this problem suddenly start or was it intermittant for some time before being an all the time thing? If so, (and even if not) you might want to put aside the electrical meter and try closely examining and repeatedly plugging and unplugging every connector that comes from or that goes to that box, ESPECIALLY if one of those connectors is buried under layers of tape in the wiring harness. One of those may simply be oxidized or otherwise crudded up-you could get lucky. (if there are multiple pin connectors involved only one pin/circuit may be a problem)

I've come across this same type of age and crud (and sometimes road salt) related problem with many different circuit connectors on many different vehicles over the years. After cleaning out the connector as well as possible (sometimes a spray solvent helps) and carefully burnishing the metal contacts physically with an appropriately shaped metal tool or tiny wire brush I tend to put in a dab of dielectric grease-whether ther was some in there before or not, as it protects against future oxidation.

5. Bite the bullet and buy a new one.

P.S. I'm glad my old Ford 2000 doesn't have this problem-it uses a dash-mounted manual pump shut off cable.

 

[KennyV]

goodolboydws....
Will NOT work this way...
Removing the power will NOT shut off this system.

It uses a fuel shut off solenoid... That solenoid shuts off THE RACK... not a pump.
You don't want to starve out the injector pumps to shut down an engine...
You 'could' use a "Red Knob" kill cable, like the older Kubota's tractors had... Matter of fact newer ones have that PLUS the shut Off Solenoid.

The combination box is just that... a combination of several things... ONE of those things is a timed out put for the shut off solenoid when you turn the key to off.
It is obviously doing the other things, but grinding, or dissolving the potting material will damage the circuit board , IC's or other components on the CB...They are potted to prevent vibration damage and to act as a heat sink... When they fail, it is a choice of replacing the complete item, or work around the function that has failed...
Two workarounds, for this particular failure would be:
1. Install a N-O momentary push button switch to apply 12volts directly to the solenoid...(push & hold till engine stops).
2. Install a pull control 'kill cable', attached to the same point on the Rack that the solenoid is now connected.
Replacing the combination box is the best choice, because you will then not 'accidentally' leave the key ON after killing the engine, leaving you with a dead battery ... :smile:KennyV

 

[reddragon]

i agree....plus.. a new box may prevent other problems in the future:smile:

 

[goodolboydws]

goodolboydws....


Well, Kenny, I bow to your superior knowledge of Kubotas.

And if Kubotas (this one in particular) leave the rack solenoid for the FI pumps in the on position with the result that the path of additional fuel to the pump is uninterrupted all the time that their engines are off, that's another story. I'd thought that someone must have made a typo in the thread and had read it as actually being the other way.

Typically the gold standard for safety would have a fuel control solenoid always be in the UN-energized position disconnecting the fuel supply whenever the ignition switch is off and the the engine isn't supposed to be running. Yes the relay would tend need to be heavier to last as long if it's wired in such a way that it's conducting power all the time that an engine's running, and more prone to eventual failure for that reason, BUT it would be safer to have an engine that doesn't start than one that doesn't stop...... Sounds like a rather poor design choice from a safety standpoint.


That accessory shut off cable sounds good-I'd forgotten to add it to my list... I'd think of it as an "improvement" rather than a "workaround" though. (One less thing on-board to fail electrically. )

And you're right I suppose for someone who's heavyhanded, grinding instead of using a purpose-designed cutting wheel in a Dremel type tool properly could potentially cause vibration induced damage.

As I said earlier, I'm glad my 42 year young Ford 2000 diesel doesn't depend on any electrics to control it's fuel flow to the pump (either on or off).
Sometimes an elegant soution (elegent in it's engineering sense=simpler) shouldn't necessarily be abandoned, in this case it's apparently being done because Kubota or the Federal powers higher up the food chain thought enough people would be too dumb to be able to remember to simply pull a cable to the on/start/run position when starting the engine and then return it to to off position later and then back on again the next time. (That wouldn't surprise me seeing how the newer cars require less and less attention or input from drivers every year, and those vehicles have fewer and fewer serviceable parts too, many things now needing to be replaced rather than being maintained-which reflects on the apparent perception of the quality of available mechanics too.)

Does Kubota actually use a full submergence type internal potting of all of the individual components within the control module itself, or is this module's body/case only hermetically sealed with an external epoxy coating to protect it from external introduction of water and other environmental contamination? From the "several cracks" comment that the original poster had made, full encapsulization doesn't sound as likely.

For those who haven't heard this before:
For heat transfer purposes a module often has either it's own heat sink being a part of the case or is attached via a relatively large contact area connection to an external metal heat sink surface, and between which surfaces is sometimes used a dielectric grease to ensure good contact, (this was commonly done with automotive ignition control modules for one example, and the engine compartment mounted modules tend to fail early if the grease layer was left or forceably washed out-can you say "careless use of a pressure washer"?).

When the primary concern is dampening vibration, modules often use either a semi-free suspension of components with cushioning (perhaps taped to wires in a wire harness) rather than having them be attached directly to a rigid piece subject to heavy vibration, or by using some sort of rubber-type isolation if being directly attached to a solid surface subject to such vibration.

Potting individual electronic or electrical components within a matrix of any solid, fairly non-resiliant material such as most epoxy recipies does very little if anything to dampen internal vibration of individual components to any significant degree-other than to possibly help retain the components themselves to a circuit board or internal connector. And doing this increases the possibility of causing a different problem

There are other materials available, but when using epoxy as a potting material it's most typically used as an insulator rather than a conductor, so it would more often than not tend to trap heat in the area immediately surrounding each individual component-with no way to disperse that heat, which would tend to magnify any overheating problem limited to a single component-or to everything inside the module's case for that matter. If overheating is not an issue for any of the components, (and especially if there is no relay/solenoid inside) full encapsulization might make more sense.

Modules are typically sealed externally or internallly, seldom both-but typically for different reasons.


thanks

 

[KennyV]

Kubota has used both:
the energized at shut off, timed solenoid ...
and the always energized hold 'ON' solenoid...where power is removed and engine shuts off.

The hold ON type is a bit more expensive, and can easily incorporate murphy type gauges... allowing an automatic shutdown if oil pressure or temperature gets out of control. This type is actually two solenoids in one... there is a pull, high current side, to overcome spring loads... AND a Hold, low current winding that will keep the fuel turned on ...

The fuel shut off is just triggered with several seconds of power whenever the key is turned off, simple timed pulse, to a 'relatively' economically priced solenoid...
Problems come up when you are accustomed to one type or the other & are not aware there is a similar but opposite working system...

As to potted circuits... I work with medical electronics and there is a variety of types of potting, I have not found any thing that was really practical to de-pot.. other than out of curiosity.. it is not worth the time to attempt in most situations... If I had this type combination box, I would most likely assemble a circuit that would perform this single function and piggy back it to the existing box.. Much easier than de-pot and try to repair....:smile:KennyV

 

[djrussell]

Does Kubota actually use a full submergence type internal potting of all of the individual components within the control module itself, or is this module's body/case only hermetically sealed with an external epoxy coating to protect it from external introduction of water and other environmental contamination? From the "several cracks" comment that the original poster had made, full encapsulization doesn't sound as likely.

There's a pic on page 2 of this thread.

 

[goodolboydws]

Kubota has used both:
the energized at shut off, timed solenoid ...
and the always energized hold 'ON' solenoid...where power is removed and engine shuts off.

The hold ON type is a bit more expensive, and can easily incorporate murphy type gauges... allowing an automatic shutdown if oil pressure or temperature gets out of control. This type is actually two solenoids in one... there is a pull, high current side, to overcome spring loads... AND a Hold, low current winding that will keep the fuel turned on ...

The fuel shut off is just triggered with several seconds of power whenever the key is turned off, simple timed pulse, to a 'relatively' economically priced solenoid...
Problems come up when you are accustomed to one type or the other & are not aware there is a similar but opposite working system...

As to potted circuits... I work with medical electronics and there is a variety of types of potting, I have not found any thing that was really practical to de-pot.. other than out of curiosity.. it is not worth the time to attempt in most situations... If I had this type combination box, I would most likely assemble a circuit that would perform this single function and piggy back it to the existing box.. Much easier than de-pot and try to repair....:smile:KennyV

-------------------------

Thanks Kenny, I learned something today and it isn't even noon.

So, they really do leave the fuel supply uninterrupted while the machine's power is off. Interesting.

I'd missed the photos, but now from what appears to be rust that I saw, it would seem that rain or cleaning water or just too much condensation is getting to this control's location and that it probably takes too long to dry out passively when the machine is not being used, so the partial encapsulization appears to make sense, while leaving the majority of the individual component bodies exposed to what may well be an inadequate air flow path. (maybe add a spacer washer at each mounting lug if/when that module gets replaced?)

I'd also examine the connector VERY closely under magnification to check for oxidation or simple looseness and evidence of possible internal arcing on one or more of the pin/socket pairs. (and if water is getting to and infiltrating that connector that could help explain someone's reference to a tech's comment about this module needing replacement often.) After seeing that apparent rust, I'd be concerned that water might be getting to and/or staying too long at other electrical component locations as well.... and inspect all connectors and leave them with a generous coating of dielectric grease inside to keep moisture out.

As to it being impractical to de-pot something, when you get right down to it, a lot of what we tinkerers/fixers/experimenters/re-designers do is impractical-at least in terms of OUR labor time involved in doing it. Doesn't your "personal" solution fall into that category-and run somewhat counter to your earlier advise on why to replace the module? I believe that one of the things that the original poster had expressed concern for was the cost of the replacement part-but he doesn't seem to be averse to spending time on the project.

 

[stoneyrunmiller]

Here's something I once ran across, with the starter solenoid I thought was bad, but it turned out not to be grounded. Can you check the continuity between the solenoid and the ground at the battery, if this happens to be the problem, a good fix is a lock washer between the solenoid and the frame.
Hope it's something simple like this!!!

 

[mrficxit]

Thanks for all the input guys. I must admit I haven't taken the time to order a new combination box yet. I was just not ready to pull the trigger yet because I didn't think I had done everything to rule out other possibilities.

However, it has just been SO HOT here in Oklahoma for the last several weeks and I just haven't taken the time to check on it lately. And luckily, with this heat and no rain, the bermuda grass isn't growing.

Since I will have to unravel all the electical wiring cabling anyway (to replace the combo box), I plan on doing that first to check all the connections going to that box. KennyV, I like the idea of just adding a separate relay to do what needs to be done to shut off the solenoid, and bypass that infernal combo box altogether. But I'm just not that electrical circuit savvy to do that on my own. But I'm willing to give it a try.

Thanks again.

 

[KennyV]

You can do this a few ways...
1. The easiest...
all you will need is an inline fuse (10 amp should do) a push button, single pole, normally open, switch, preferably weather resistant. A little 14 gauge wire. A spade OR bullet connector, that matches the hot wire going to the fuel kill solenoid....

Wire from an always on 12 volt source, through the inline fuse, to the push button switch, then to the wire pig tail on the solenoid. Whenever you need to kill the engine simply push the button and while you are pushing it 12volts will be applied to the solenoid...

This will work perfectly, but you stand a chance of leaving the key in the on position, and coming back to a dead battery later...

In the 2nd method... You can place a relay in the add on 'system', it will prevent you from killing the engine with the push button, Unless the key is in the OFF position...
If you want to do this second method instead of the first... Let me know and I'll draw a wiring diagram... :smile:KennyV