B7800 won't crank

Barneyhunts · Jul 10, 2008

I was working with my B7800 today and I got off the seat with the engine running and walked away from the tractor. When I walked back the engine was stopped and would not crank. I checked to insure the PTOs were not engaged and they were not. I thought a limit switch might have failed so I checked the seat switches (2) and the PTO switches (2) and found that the seat switches are OK, but one of the PTO switches is not closing,i.e. it is not closing to indicate the PTO is disengaged. I jumpered this switch but the engine will still not crank. I get the lights on the dash, and I can hear the fuel solenoid, but the engine does not crank. This happened this evening so I haven't had a chance to call my dealer. Has anyone dealt with a similar problem? Does anyone have a wiring diagram for this tractor (B7800) that he can post? I'd like to determine what else needs to be satisfied B4 the engine will crank. Any help or suggestions would be appreciated. I was doing loader work B4 I stopped and left the tractor.
Thanks,
Barney

Ob1kubota · Jul 10, 2008

Was the brake set when you got off the seat?

crbr · Jul 10, 2008

One other thought (been there).....The HST pedal needs to find its home in the neutral position. Rock the pedal with heel / toe or by hand to help it find it's neutral position, or tap it a few times and allow it to return to its middle position.

This is a fairly common problem with the B7800. If this is the case, warranty should replace the safety switch.

Barneyhunts · Jul 10, 2008

OB1, the brake was set when I left the tractor, but I didn't raise the seat which was one reason I suspected the PTO.

Crbr, I'll try rocking the HST pedal tomorrow. I hadn't thought about that.

Thanks for the prompt feedback,
Barney

JOHNTHOMAS · Jul 11, 2008

I had the same problem with my B7800. I applied dielectric grease to the seat switch connections. The next year it done it again just as you described and I checked seat safety switches and they were OK. Finally got it to start by rocking it as I was headed down hill when it stopped. One time I was on flat ground and it done it. Wouldn't start so I pushed clutch pedal in hard and it started but next time that didn't work. .Kubota mechanic told me it was probablythe HST pedal not centered. I probably bumped the HST pedal when rocking and when pushing in the clutch hard. After that I would toggle the pedal before trying to start and had no more problem until I traded the tractor a couple months ago. If it does it again, move your HST pedal and make sure it's centered.

Barneyhunts · Jul 11, 2008

It appears to be the HST pedal. I checked the switch on the pedal and it is not closing(the switch should be electrically closed when pedal is in mid-position) all the time unless I move the pedal in reverse. My dealer advised me to try and lube every pivot and connection on the pedal. I put an electrical jumper on the switch and the engine cranks and runs fine.
Thanks JohnThomas, Crbr and OB1 for taking the time to help.

Barney

rickster · Jul 11, 2008

Had that happen to me also

CompShooter · Jul 11, 2008

Just the other day I swas removing my rake when the tractor stalled and wouldn't start.

While working with 3ph attachments, I leave the tractor running, get off and stand to the side while wrestling with the attchment. At some point I usually have to raise or lower the arms or move the tractor forwards or backwards. I always stand to the side of the tractor and try to be as safe as possible.

Back to the other day. I just finished removing the rake but I had to move the tractor forward to clear the attchment. So I did what I have done since I've owned the B7800, I pressed the HST pedal forward.

At the same time my wife was talking to me and all of a sudden the tractor quit. I thought that was strange, it never done that before.

Then for some reason my wife wants to ride the tractor across the yard. She jumps on but it won't crank. She tried 4 or 5 times. Finally when I was about to kick her off it started. Until reading this thread I just thought maybe she didn't have the clutch fully depressed. But now I believe it may have been the HST pedal position.

So let me get this straight. If the tractor is running and I jump off, if the pedal is depressed it will stall? I suppose in the past I only slightly depressed the pedal since I only had to move the tractor an inch or so. Good informaiton to have, thanks.

JOHNTHOMAS · Jul 12, 2008

Compshooter:So let me get this straight. If the tractor is running and I jump off, if the pedal is depressed it will stall?
I don't think that's what we are saying. What I'm saying is that if your B7800 won't start then rock the HST pedal to make sure it's centered. I don't know if it will stall if your not on the seat and push the pedal. Traded my B7800 so can't check that. Try it and see but I don't think it will. My problem was always when trying to start it after using it or even when a new day start sometimes.

Barneyhunts · Jul 12, 2008

If I get out of the seat and try to move the tractor by pushing the HST pedal the engine quits. If the pedal is in the mid position it will start back up again.