Kubota L2250 Diesel tractor - Engine turns only 1:10 times the key is turned

[LivingLodge]

Hi all,
We have a Kubota L2250 diesel tractor that will usually not crank at all. Turning the key makes the dash lights dim slightly, but usually nothing else. The battery is charged. A voltmeter on the battery terminals (wire side) shows 12.5 volts in on position, 12.15 volts in start position when the tractor does not start. Put a voltmeter between ground and the trigger lead of the starter solenoid - 0.0 volts in crank when it does not start, and didn't pay attention to the voltage when it did start since: 1) didn't seem important since it started, and 2) I had a loud running diesel in my face. The success rate seems random, but is only about 1 in 10. I've tried wiggling the shift levers in their neutral position in case there are safety switches there. We tried pulling apart the push-terminal blocks and pushing them back together in case there was a corroded connector.

The starter solenoid trigger lead comes from a wire bundle near the starter, and from near the same point comes a pair of red wires that lead to a white plastic push-terminal block. The other side of this block has a loop of blue wire that gets warm while trying to start the tractor. Since it is a loop of wire that simply shunts the red wires, I assume it is a bypass or test point of some sort. Can anyone tell me what this is?

Can anyone provide some guidance in debugging this tractor?
Can anyone tell me where I might find a wiring diagram or other useful documentation?

Thanks,

Scott

 

[SPYDERLK]

It may be the start position on the ig switch. Try turning it less forcefully. Maybe wiggle the key.

 

[kuboman]

Try bypassing the ignition switch and run a jumper to the starter solenoid from the battery. If that will crank the engine with regularity then your ignition switch is the problem. If no joy then your starter solenoid is toast.

 

[Coyote machine]

You could have a bad ground cable from the battery to your frame/chassis. Check the tightness and cleanliness of both ends of the negative cable AND the positive connection at the battery. When/if it starts again read the battery voltage, it must be higher than your static readings; between 13-14.25volts being returned to the battery, depending on load. If the ground cable seems compromised put a jumper cable from the negative post to a clean bare metal chassis ground to see if it starts. If it does, then the cable is toast.

 

[LivingLodge]

I've not done it enough times to be sure of cause and effect, but it seems that moving the clutch pedal gets the beast to crank.

 

[rbargeron]

Hi all,
......... from near the same point comes a pair of red wires that lead to a white plastic push-terminal block. .... I assume it is a bypass or test point of some sort. Can anyone tell me what this is?

Scott that loop is the fusible link. The fine wire gets corroded and may not pass the solenoid current. Part number is 38430-34530 around 7 bucks at a dealer. You can temporarily replace the loop wire with a piece of copper house wire to see if that's the problem. The fusible link is there to protect the instrument panel if a battery gets connected backward (don't connect a battery backward while the link is defeated

 

[SPYDERLK]

I've not done it enough times to be sure of cause and effect, but it seems that moving the clutch pedal gets the beast to crank.

The 2550 clutch must be depressed to start. Yours is probably the same. That switch may be acting up.

 

[rbargeron]

Agreed, the clutch pedal switch may need attention. The wiring connectors are set up so it's possible to plug the leads together, bypassing the switch. Be sure its out of gear !

Edit - here's a L2550 & L2250 wiring diagram - (small scanner so 3 pages)