RK25 fuel shut off solenoid won't allow engine start

[K5lwq]

Normally there will be two relays for a stop solenoid with 3 wires. One for the pull circuit and one for the hold. The pull relay normally will get the ground for the coil side through a safety control module. Not having a wiring diagram makes it more challenging but not impossible. I would start by checking all fuses and check all the safety switches are making.

 

[Gator6x4]

In a system as described there are usually four electrical parts. 1. Fuse 2. Fuel Solenoid 3. Relay 4. Controller.

The fuse provides current to the relay which provides voltage to the controller. The controller provides battery voltage to the solenoid when the switch is turned to the start position this retracts the fuel solenoid plunger. When the key is released to the run position from start, most times, the controller supplies lower than battery voltage to the fuel solenoid to keep the plunger retracted to allow the fuel rail in the injector pump to remain in the open position to allow fuel to flow.

Look at the wire colors at the solenoid and follow the wiring harness containing the wire(s) and look for a small white electrical box(I said white because most are-yours may be green, blue, black etc) If you locate the controller with the switch in the on position you should have 12 volts on two of the electrical connectors. Turn the switch to start and you should then have voltage on the other post which would retract the solenoid plunger.

 

[crofutt]

Hello, I have a 1-1/2 yo RK 25 that won't start. The shut off solenoid, when the key is on should retract. I replaced the solenoid thinking it was bad but the new one is the same way. If I push the plunger in, it stays in until turned off then it won't retract. I've been removing the solenoid, turning on the key, push the plunger in then reinstall the solenoid. I can run the tractor until shut off, then won't start.
RK doesn't supply a wiring diagram even to their mechanics at their stores. If I had one maybe I could figure something out. There are 3 wires going to the solenoid, 12 volts when the key is on one wire, other two have no voltage (assuming one is the negative). But that 3rd wire may be something to troubleshoot but... No diagram...
Anyone else had this problem or have a suggestion what to try next? Or knows how to get a wiring diagram.
Thanks
Bill

Problem solved!

The circuit that energized the fuel shut off solenoid is the same as the starter solenoid. No separate controller for the fuel solenoid. The hold circuit does have its own relay.

There is a fuse in the circuit, no mention of it anywhere in the manual. Location is on the battery box tractor front. That fuse, turned out, was the problem. Once I found it, I tested it first with an ohm meter which showed it was ok. I then tested with a test light and there was current on the load side of the fuse so, all seemed fine but no current was getting to the solenoid. I had the fuse in and out several times over the last couple days so today I decided to run a new wire from the fuse to the solenoid. It didn't work and now there was no current on the load side of the fuse. I pulled the fuse again to test it and sure enough, it showed continuity... Then it didn't. What? I looked very close at the fuse and could see the fuse was actually broken, not blown. Wiggle it a little and it makes contact. I've (hopefully) attached a couple pictures showing the fuse being tested.
What a pain only to find out there's a "secret" fuse and it was the problem. Spare fuse in tractor tool box now...
I have thousands of hours working on GA airplanes and motorcycles. Never seen a fuse do this.
Thanks much to everyone who supplied information. It was very helpful in finding the rather unusual problem.
Bill

 

[LittleBill21]

get a real meter please, those are very very dependent on a good battery in the meter for being remotely accurate.