B7800 shutdown

[iamhistory]

So my 7800 just shut off the other day and I haven't been able to start it since. It shut off abou 15 minutes before that and started up with no problem. Once it shut off this time, that was it.

My son was sitting on the seat and I was putting some wood in the bucket and it simply turned off. I was sure that it was just a safety switch somewhere but I am now stumped after a week of not being able to figure out the problem.

I've read every thread I could find on what the problem could be and what other guys have experienced and I've tried everything they did: seat switches, jumping the terminals, checked fuses, checked pedals, checked gear levers, charged the battery, etc.

I can't figure it out. I have lights but no turnover when I hit the key. It has 346 hours on it, has had no problems and it is well maintained. It was running like a champ for an hour or so before the shut off and now it's sitting there.

Can anyone help me out with some ideas? It's probably something simple but I'm stumped.

Thanks guys.

 

[RoyJackson]

Have you tried jump starting from a known good battery (that may have been what you meant by "jumping the terminals")?
Old batteries can take a charge, but they may not hold a charge (as soon as you start cranking, the battery is drawn down). A bad battery is what it sounds like since you have lights, but no cranking.
Another thing to consider is a bad ground at the battery or the starter. Definitely check where the grounds connect to the tractor's frame.
Good luck!

 

[BlacknTan]

There was a thread about this recently, and I can't find it, but there is another switch with a plunger down near where the hydraulics return to the tank. The plunger seems to get sticky and cause this problem

I'll keep looking for the thread..

 

[BlacknTan]

Here's the thread..

Herringchoker figured it out..

Hope it helps.

http://www.tractorbynet.com/forums/kubota-owning-operating/153385-kubota-7800-wont-start.html

 

[grsthegreat]

I'm not sure about the Kubota series, but most other tractors have a MAIN fuse located near the starter....a 50-60 amp fuse. have you checked this fuse also???

Also, have you determined that its getting fuel past the fuel pump before the injector pump. There is also a stop solenoid that may be stuck.

 

[BeezFun]

Since you have lights but no crank, I'd pull the battery and take it to battery place, they'll test it for free with a load on it. If it passes the test, bring it home and jumper it right to the starter to see if it turns over. If it does, you've got a bad cable, connection, ignition switch problem, etc. If battery doesn't pass load test, get a new one and that should fix it.

 

[iamhistory]

Ok, so here we are two weeks later and my tractor is still sitting. I have made some progress with it and got it started but it will not stay running.

It was not the fuses. It was not the battery. The safety switches and seat switches are showing they are working properly. The fuel solenoid was shut off and jumping the starter would not start the tractor b/c of not having fuel. The relay in the dash was taken out and tested to find that it was fine. We also tested it overnight under a load and it was still fine. Called the dealer and he told me it was the voltage regulator (without looking at the tractor). And we were getting pretty well stumped.

I started playing with the switches and wires this weekend and heard an audible "click" when I turned the key on and off. That "click" was no previously heard. It turned out to be the fuel solenoid (I think) and when I heard the click and jumped the starter, the tractor fired right up. It would run but if I got off the seat even in neutral the tractor would shut off. I bypassed the seat switch and put a jumper wire on so I could get off the seat and the tractor would still run. I actually was able to mow my grass this way for about an hour.

Suddenly, the tractor shut off again and would not start back up. I had no fuel. I went out the next morning, the ignition "clicked" again, I jumped the starter and fired her up. Had fuel and even hauled some wood around. Suddenly again, she shut down and has been that way for two days.

I can't figure it out. It seems like one of the switches is telling us that the mower deck is engaged but we have tested them, checked the plungers, checked their contact, etc. and really can't find anything wrong. But something is shutting my fuel off and it has to be a safety switch somewhere.

Any ideas from my update? This is driving me nuts, not to mention, I need the tractor to run dependably because chores are piling up.

 

[iamhistory]

I should also mention that I cannot start the tractor with the key. We tested the ignition switch and it is working properly. The key turns and shows all lights, accessories and glow plug are good to go but it just won't start the tractor. Nothing happens........no turnover attempt, or anything.

I have to jump the starter to start the tractor. As mentioned, it doesn't stay running. We checked the ground and all wires for being loosed, broken, etc. We didn't find anything suspect and I'm running out of ideas of things to check.

What the heck could this be? I'm guessing it is something right under my nose and relatively easy to handle.

 

[grsthegreat]

well the fact that the key wont start it i think it HAS to be a safety switch somewheres. They have them on the PTO, the seat, the clutch and sometimes on the gear shift/HST levers.

If the key switch checks out OK, the signal is being cut between the key and the starter. Jumping it is bypassing that. Now that it isn't starting does the stop solenoid still click when the key is turned?

I had to just recently replace my stop solenoid for this same reason...no click when key is turned, and no fuel to tractor.

 

[Motractr]

I should also mention that I cannot start the tractor with the key. We tested the ignition switch and it is working properly. The key turns and shows all lights, accessories and glow plug are good to go but it just won't start the tractor. Nothing happens........no turnover attempt, or anything.

I have to jump the starter to start the tractor. As mentioned, it doesn't stay running. We checked the ground and all wires for being loosed, broken, etc. We didn't find anything suspect and I'm running out of ideas of things to check.

What the heck could this be? I'm guessing it is something right under my nose and relatively easy to handle.

There is a safety switch on the forward/ reverse pedal below the floor board. To check, put the trans in neutral and rock the pedal back and forth while turning the key with the clutch depressed. Also, the seat switch always gives me problems. The pedal switch is kind of hard to see. Also, check the 5 amp keystart fuse. I keep extras on hand because they blow every once in a while.

 

[iamhistory]

Just an update on this situation:

I've been running my tractor since my last post by jumping the starter. The key will click when turned on but will not turn the tractor over. I turn the key on and use a wire to jump the starter. I use the tractor and it works like normal until I turn it off. Then I have to do the same things over again to start and run it next time.

I did track the problem down to the fuse box area where the wires comes out of the firewall near the fuse box. When the tractor is running and these wires are moved around, the tractor stalls. So when I would jump the starter and run the tractor, hitting bumps or something would stall the engine.

Once I tracked it down to those wires in that area I simply positioned and zipped tied the group of wires so they would not bounce around and now it has only stalled twice in 4 months while running.

I hate the fact that I can't figure out what's going on and I really want to get this fixed. The dealer though wants hundreds of dollars to bring it in and look it over and I hesitate at doing that. It's gotta be a bad switch or fuse somewhere and possibly a short. I just can't track it down completely. No fuses are blown and all safety switches have been tested, sprayed, toyed with, rocked back and forth, etc. etc. and still nothing. Besides replacing every switch, I have checked everything suggested and thought of.

I've narrowed it down but haven't nailed it yet. Good enough for now but it really bugs me.

 

[BeezFun]

Once I tracked it down to those wires in that area I simply positioned and zipped tied the group of wires so they would not bounce around and now it has only stalled twice in 4 months while running.

Wow man, I feel your pain. Thanks for posting an update on what's going on. Sounds like you've diagnosed problem to intermittent connection in loom near fusebox/firewall. Could a mouse have chewed through wiring and you can't see it? Or since it's coming through the firewall, maybe the insulation got rubbed off the wires? I think I'd loosen that loom, separate the wires and inspect each one, and start wiggling them one by one right up to the fuse box to figure out which one is bad. I would guess it's possible the starter solenoid is also getting intermittent connection from this fusebox area, which might be why you can jump start it with a wire but it won't crank with the key. If you find the area where there's a problem, I'm guessing you'll solve both your problems.

 

[crazyal]

I think what you'll need to do (or your dealer could do it) is pull the wire harness and inspect it. I'm sure your dealer would just replace it with a new one but if it was me I would just find the problem and fix it myself. I'm guessing that you may have a broken wire, maybe from a mouse, a stick or something, or chafing. Another option could be that the insulation got damaged on one of the wires from rubbing on something and when it moves it shorts to ground or to another wire. There's also the chance that a connector that's crimped onto the end of a wire is loose or poorly crimped. Either way I think you're going to have to take it apart to find the root cause of the problem.

 

[gengine]

Sounds like your not getting power from the key to the switch terminal on the starter. If you are jumping from the bat. Terminal to the switch terminal, then your starter solenoid is fine. If your jumping the two large terminals, then you haven't ruled out the solenoid. If you find it's not the solenoid, the wiring behind the fuse box is your big clue. Wether it's the solenoid or not, the intermittent short still needs fixed. That in itself may be keeping it from starting with the key.

 

[gengine]

I just read another post of an in-line fuse on the key switch of another kubota. Maybe something to investigate...

 

[wcampbell47]

Had a similar problem with my B7510 bought in 2007. Run a jumper wire from the hot side of the battery to the wire on the fuel solenoid. When you connect you will hear a click. With the jumper wire in place my tractor ran until I removed the jumper wire. Dealer ordered the "computer" that is under the dash. Came from Japan. Issue solved.

In your case look for a broken wire. When the unit is cold the insulation contracts enough for the wire to make contact. The unit heats up from running, the insulation expands and the wire loses contact. Many years a go an old Massey Harris had a broken spark plug wire that we finally found.

Just saying .....