I have a Kubota L3940 that burned up the fuel solenoid with 49 hours on it. It's out of warranty due to being a 2012. I replaced it and 6 hours later it melted down the 2nd one. The previous owner had no problems with this tractor. The only thing I do differently is that I use the auto throttle. He said he didn't know what that was. The tractor looks like new and has always been stored inside. I've looked over the wiring and can't find anything out of the ordinary.There is no rust or corrosion anywhere on it. Is there a relay or something that I should be looking at? The 3rd one is arriving today but I don't want to install without fixing the original problem.
L3940 melting fuel solenoid
- Thread starter Spyderrob
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North Idaho Wolfman
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That model has an OPC Controller that controls the solenoid, so not just a simple relay.
Reasons that the solenoid could melt down is from too much resistance on one of the wires, most likely the ground wire.
That solenoid i do believe has two coils, a pull in coil and a hold coil, and excessive resistance on the ground will make it get very hot, very fast.
It could also have two high of resistance on the hot wires, but that is less likely.
Was the solenoid that you purchased, bought from kubota or another source?
What is the part number of the solenoid that you are getting?
Reasons that the solenoid could melt down is from too much resistance on one of the wires, most likely the ground wire.
That solenoid i do believe has two coils, a pull in coil and a hold coil, and excessive resistance on the ground will make it get very hot, very fast.
It could also have two high of resistance on the hot wires, but that is less likely.
Was the solenoid that you purchased, bought from kubota or another source?
What is the part number of the solenoid that you are getting?
Daren Todd
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It may be wise to just run a new ground to it. You'll need to figure out which wire is the ground, and splice into that wire. Leave the original hooked up.
But find a bolt close to the solenoid, clean it up good to bare metal. Then connect the ground to that bolt. On my equipment at work, I'll attach the ground wire to a bolt on the injection pump.
Check your quick connects in the wiring harness for moisture and corrosion as well.
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But find a bolt close to the solenoid, clean it up good to bare metal. Then connect the ground to that bolt. On my equipment at work, I'll attach the ground wire to a bolt on the injection pump.
Check your quick connects in the wiring harness for moisture and corrosion as well.
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North Idaho Wolfman
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Depending on connector type, the wires could be inadvertently reversed. This would energize the pull in constantly, where it needs only a momentary activation during crank. Then the hold circuit remains on while running.
It is also possible that something is preventing the solenoid from pulling in all the way. That can cause much higher current flow through the coil.
There are only 2 wires going to the solenoid. I tested them today and both are 12 volts. I tested the new solenoid. I grounded the solenoid and then put 12 volts to each of the posts. It would not retract unless 12 volts was put to each of the posts. As soon as I removed the voltage from one of the posts it extended. It didn't matter which posts I removed. So I am assuming that means it needs 24 volts. But clearly the manual and the solenoid says 12 volts on it.
Any suggestions what to try next? I'm 100% confident that I could install on the tractor right now and it would run just fine. But I am concerned that after a few hours it would burn up another fuel solenoid.
Any suggestions what to try next? I'm 100% confident that I could install on the tractor right now and it would run just fine. But I am concerned that after a few hours it would burn up another fuel solenoid.
As noted previously, 2 wire stop solenoids should only get power to the "pull in" terminal for short duration. If the pull in is constantly energized then it will burn out.
The wires in the harness are generally different, pull in is slightly bigger.
General resistance, about half ohm for pull in, 15~20 ohms for hold in.
The wires in the harness are generally different, pull in is slightly bigger.
General resistance, about half ohm for pull in, 15~20 ohms for hold in.
North Idaho Wolfman
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The 2 wires are pull in power, and hold power.
Put ground to the case and power to one of the two leads and it will pull the coil in.
Then with the coil pulled in you put power on the other lead (hold coil) and cut power from the other (pull in coil) and the coil should stay pulled in until you remove power.
So on the tractor side of things with the key in on position you should have power to one wire, that will be the hold coil wire, then when you crank you will get power to the other wire too this will be the pull in coil wire.
If with the key in on position you get power to both sides there is your issue and that will burn out a coil every time.
Issue will most likely be in a bad or stuck closed relay or key switch.
FYI: 12V on one lead and 12 volts on the other lead will not give it 24 Volts, just 2, 12 volt feeds.
Put ground to the case and power to one of the two leads and it will pull the coil in.
Then with the coil pulled in you put power on the other lead (hold coil) and cut power from the other (pull in coil) and the coil should stay pulled in until you remove power.
So on the tractor side of things with the key in on position you should have power to one wire, that will be the hold coil wire, then when you crank you will get power to the other wire too this will be the pull in coil wire.
If with the key in on position you get power to both sides there is your issue and that will burn out a coil every time.
Issue will most likely be in a bad or stuck closed relay or key switch.
FYI: 12V on one lead and 12 volts on the other lead will not give it 24 Volts, just 2, 12 volt feeds.
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So,if key is on and theres 12 volts on both wires that connect to solenoid,then there is your problem. One wire powered while running, two wires powered while starting.