Kubota 4310 will not turn off with the key, new relay and solenoid, voltage problem

ecurbbruce · Jan 4, 2019

Hi, New member here.

I have a Kubota L4310 GST. Last year the key stopped turning the tractor off. I removed the fuel shut off solenoid and put it back on and it began working again. (I don't know why) It stopped working again. I saw the rubber boot was torn so I bought a new solenoid. It still did not work, so I checked the voltage at the solenoid. I saw random voltages most of the time under 12 volts. If I saw 12 volts using the meter I would plug the solenoid back in and it would not work. I would unplug it and check with the meter and see less than 12 volts.

This tractor has a single wire that goes to the solenoid, it is supposed to send power to the solenoid for 5 seconds when the key is turned off.

Under the dashboard is the relay for the solenoid. I have checked the connections on all the wires with plugs that separate, as well as the fuses in the box by the left foot. I found that after messing with the connections I was still getting random voltages. I unplugged the relay for the solenoid and jumped 12 volts to it. It actuated like it was supposed to do. I thought the relay had gone bad, I bought a new relay. Not the fix, I still have low voltage.

The voltage out to the solenoid is consistent at 9 1/2 volts, it lasts for 5 seconds when the key is turned off. I found the hot wire bringing 12 volts into the relay and found that when the glow plug is on, (1 click with the key) the voltage drops to 10 volts, when the glow plug is done the voltage returns to 12 volts, then when the key is turned off, the voltage drops to 9 1/2 volts for 5 seconds. Sometimes it is 9.6 sometimes 9.5 volts and it very slowly drops during the 5 seconds.

Has anyone run into this problem? Suggestions on what I should do next?

Thanks

diesel85 · Jan 4, 2019

Random voltages sounds like a chaffed wire. I'd trace the lines out.

Ertaious · Jan 4, 2019

I too have just experienced similar problem with my bx1860 ignition switch not killing the motor when switched off. I’m curious to hear what people have to say about this. Maybe it’s just a bad switch.

diesel85 · Jan 4, 2019

^

Could be that too, especially since the relay has been replaced.

You could try disconnecting the battery, and try using a DMM and ohm everything out. See if you get fluctuations then pin point it.

Eddie1955 · Jan 5, 2019

First i would clean the battery and make sure you have 13+ volts in the battery when disconnected. Then ptu your meter on the key switch plug to the wire going to the relay (not on the relay or solenoid), if you have good voltage there with key on the off your problem move to the relay and check input and output wires for 12v. My guess would be a bad wire connection or bad connection inside the key switch, either way you will have found the source of the low voltage problem.

ecurbbruce · Jan 5, 2019

Eddie 1995 here is an update.

I have 12+ volts on the back of the key switch. There are 2 red wires that go to the key switch, one is just energized when the glow plug heater is on. The center wire is hot all the time. On this center wire I get a drop to 10 volts when the glow plug is on, then it goes back to 12+ volts, when it's turned off it remains 12+ volts, no drop other than for the seconds the heater is on. I then move to the 12v into the relay. I get 12+ volts, when the heater is turned on it drops to 10 volts for the few seconds, then when the heater turns off, it goes back to 12+ volts until the switch is turned off, then it drops down to 9 1/2 volts for the 5 seconds it would be sending power to the solenoid. (the solenoid was unplugged to rule it out as a problem)

The wire harness is wrapped tightly with electrical tape inside the flexible black plastic protective outer cover, so trying to isolate a single wire has not been done yet, I fear it would do more harm than good removing all that tape.

So I can see a solid 12 volts to the key switch that does not drop when the key is turned off. The relay has 4 wires, 12volts, ground, wire to the solenoid, the 4th wire is a millivolt until the key is turned on, it goes to 12+ volts until the key is turned off, it immediately drops to a millivolt. I am guessing that is what triggers the relay to send power to the solenoid, the relay is a timer so that is why it sends power for 5 seconds. I still do not know where 2 1/2 volts are being lost. From the key switch to the relay there is some other connection I cannot see. The wires to the relay are relatively thin, all the wires to the key switch are heavy gauge.

ecurbbruce · Jan 5, 2019

PROBLEM SOLVED!!!

I isolated the 12volt feed to the solenoid all the way back to the fuse box, it was a straight wire run. On one side of the fuse was a large gauge red wire that was jumped so it fed two separate fuses, the other was the thin wire I traced. I started with the volt meter on the large red wire, there was no voltage drop other than when the glow plug was on. I moved to the other side (the thin wire) the voltage dropped when the switch was turned off. I had checked the fuse, and lubed the connection. It was a blue 15amp fuse, so I swapped it with another. NO voltage drop. I'll be throwing that fuse away and using a new one.

diesel85 · Jan 5, 2019

Good to know. A worn out fuse.

Eddie1955 · Jan 6, 2019

ecurbbruce said:
PROBLEM SOLVED!!!

I isolated the 12volt feed to the solenoid all the way back to the fuse box, it was a straight wire run. On one side of the fuse was a large gauge red wire that was jumped so it fed two separate fuses, the other was the thin wire I traced. I started with the volt meter on the large red wire, there was no voltage drop other than when the glow plug was on. I moved to the other side (the thin wire) the voltage dropped when the switch was turned off. I had checked the fuse, and lubed the connection. It was a blue 15amp fuse, so I swapped it with another. NO voltage drop. I'll be throwing that fuse away and using a new one.

I figured you would find it by checking voltage from source to solenoid. Good work.

hoffmtc · May 5, 2020

Just to revive an old thread, and for someone's future info that might be searching this problem:
I also have a recently acquired L4310 that would not shut off with the key about a month after owning it. I was not getting 12v out to the solenoid when the key was turned off. The relay was ok as well. I had read this thread about the fuse, so I started investigating that as another possibility. My fuses were all fine, BUT I happened to notice a bit of white corrosion on the black plastic around the bottom fuse holder.

Turns out it was not the fuse, but rather the fuse receptacle holder in the fuse box. The power wires are crimped onto these receptacles from the backside. The receptacles have spring tabs that make contact with the fuse legs. One side of the fuse receptacle was missing these spring tabs, it had corroded to the point of falling off. No contact on that side of the fuse, no 12v being sent out to the shut off relay.

I may be able to find those receptacles and see if I can re-crimp them onto the wire if there is enough slack to redo it. But for now I have used a small length of steel wire to wedge in the backside of the fuse receptacle so that the fuse leg and what is remaining of the receptacle make good contact. It works fine now, we'll see how motivated I get to actually redo it the right way....