Kubota B7800 won't crank - intermittent fault.

Giles'

New member
My Kubota B7800 was giving problems: sometimes it wouldn't crank, or would stop when I took my weight off the seat (even when the PTOs were de-selected, i.e. not in use), and once stopped it refused to crank, though it might do so after an hour or two. At first I suspected the control unit (small black box full of electronics behind the dash). I didn't want to by a new one straight off ($114) in case that wasn't the problem, because electronic parts are invariably non-returnable.
Eventually, I found the cause: There is a microswitch (behind where your right foot comes to rest on the running board) which detects if the FWD/REV pedal is in neutral position. When the pedal is in neutral, this switch should be depressed. This is to prevent you from starting the tractor when the pedal is NOT in neutral position. If the FWD/REV pedal is pushed down (either direction) a small (about 3") rod in a metal sleeve is retracted, thus opening the microswitch signaling to the control box not to allow the starter to crank. The pedal must be in neutral position if the engine is to crank. Old grease and dirt had got between the 3" rod and the sleeve and so it would not slide all the way and thus push on the microswitch. It was gummed up! I shot a load of WD40 into both ends of the sleeve and work the pedals back and forth until the little rod was able to move freely again. Now everything works and there was no need to buy a new control box, which wouldn't have solved the problem anyway.
 

Doc

Admin
Staff member
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Wow. Tough one. Thanks for posting. I'm sure you will help quite a few others out with this post. :tiphat:
 

Jim_S

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I had the same switch go out on my L3400 a couple of years ago. Sometimes it started and sometimes it was dead as a doornail. Replaced the switch and all was fine.

Jim
 
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