B21 Fuel Solenoid.

[bill karrer]

Hello! This is my first time posting here. I have any older B21. My fuel solenoid activates when I go to the start position. The engine starts but dies when key returns to the run position. If I remove the solenoid from the pump, the engine starts and runs fine. I can easily push the fuel flow rod in and shut the engine down.
With the solenoid removed but still plugged in, and key in the run position, I can push the plunger of the solenoid in and the hold coil holds the plunger in. Now, when I turn the key to the start position, the solenoid plunger cycles out and is pulled back in. That would be fine and the engine will start. However, the hold coil will not hold the plunger in when the key returns to the run position. Thus, we have the engine starts but dies scenario.
I have tried 3 new solenoids and have replaced the key switch. I have replaced all of the fuses in the fuse box. All wires are receiving power when they are suppose to. The ground wire checks good. This is a three wire solenoid. I even hot wired the hold circuit on the Solenoid to guarantee power at all times. I still get the same results.
I am stumped. Any ideas?

 

[Carl_NH]

If you can find a wiring diagram that would help, but here's a link to Messicks B21 parts list. I suspect it could be a start relay #70? Kubota B21 (4WD TRACTOR) Parts

But that's a guess as the start relay likely closes when cranking then releases when running, and you have spent $ on replacing parts already. The pic below is the starting circuit diagram

 

[Carl_NH]

Also search TBN as there is a wealth of info here

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwilrcjIhKb2AhUOjIkEHREaAYIQFnoECAMQAQ&url=https%3A%2F%2Fwww.tractorbynet.com%2Fforums%2Fthreads%2Fb21-starts-then-stops-immediately-on-key-release.157994%2F&usg=AOvVaw0LeotVgdDh8avKZwwaB302

Or this one - did you post on Orange Tractor too? B21 won't stay started. Suggestions?

 

[thepumpguysc]

Yes, it’s not A FUSE.. it’s a RELAY that’s bad..
There should be a group of 3.. replace them all

 

[bill karrer]

Yes, it’s not A FUSE.. it’s a RELAY that’s bad..
There should be a group of 3.. replace them all

Sorry for delay in getting back with an update, but life happened and I needed to address another issue. Anyway, after considerable spark chasing, smoke checking and bench testing I did confirm that there is nothing wrong with the new solenoid and it can function properly. I confirmed this through a "bench test" by hooking directly to the battery. In this configuration, the plunger is retracted by the momentary activation of the pull back coil. The hold back coil, activated independently, does hold the plunger back when the pull back coil is deactivated. The plunger remains retracted until the hold back coil is deactivated.
Now, about those three relays. My service manual, as well as the parts manual, only list and shows a starter relay. It is mounted behind the instrument panel, near the light switch. Where and what are the other two relays? This tractor does not have an OPC. I changed the starter relay but it did not help.
I am doing some other maintenance work to the tractor to get it ready for gardening season. If all else fails, I will wire the hold back coil circuit to the battery with an inline fuse and a dash mounted on/off switch in the circuit between the battery and the hold back coil. Southern Engineering at its finest! Can I say "Southern Engineering" here? I am in the South.

 

[arto98607]

No, it's an invitation to open a can of worms.....

 

[5030]

Yes, it’s not A FUSE.. it’s a RELAY that’s bad..
There should be a group of 3.. replace them all

... and buy them aftermarket from Digikey or Dell. You don't even want to know the OEM cost and interestingly, the aftermarket ones are identical to the OEM, except for the price.

 

[bill karrer]

There is the starter relay that I installed. Same part number and manufacturer as OEM but MUCH cheaper elsewhere. Now, that relay did not solve the issue. If there is a "group of 3 relays", they are certainly loosely grouped. If someone has the part numbers of the other 2 relays, I would gladly order them and find them on the tractor.
Thanks!!!!