Small Engines (Lawn Mowers, etc.): Mower starter problem, starter solenoid, starter wire

Question
Hello BEN

I have a 1995 Grasshopper lawnmower, Model # 718, serial # 454880 with a delco starter on the Kohler engine, family 2KHXS 6242GC, DISPLACEMENT 624 CC Model # CH18S, SPEC 62621, SERIAL # 3229605071.

The starter motor will engage and start the engine but does not want to disengage when the start switch is released.

Removing the starter and testing it out on a bench I got these results;
With the starter housing grounded and power just to the solenoid (small start terminal) , no power connected to the large battery terminal of the solenoid caused the starter gear to move to the engage position, removed power from the solenoid start terminal and the starter gear retracted, working normal.

But when the heavy battery + power wire is connected to the correct terminal of the solenoid, and the start switch is operated, the starter gear moves to the engage position and the starter gear spins fast. When the start switch is released, the starter motor continues to run and the starter gear stays in the engaged position. Pulling the small start wire off of the starter solenoid does not stop the starter motor from continuing to run.
Pulling off the large + battery cable is the only way to stop it.
The solenoid gets quite warm when this happens. It looks as if power is backfeeding from the heavy starter wire of the solenoid once it is engaged and keeps the solenoid engaged.

I have tried three different starter motors and each acts the same way, one the original on the mower and the other two starter motors were brand new.
Any ideas on how to correct this problem would be greatly appreciated.

If you need any additional information, I will gladly supply it.

Thank you in advance for considering my problem.

Answer
Keith

Hit the solenoid to see if it is hanging up. with starter motor turning on its own like you described, remove any small wires from the solenoid except the battery wires to see if it may be your ignition switch hanging up.sounds like a bad solenoid to me, they're pretty cheap, I'd replace it first. Also look at the backside of your ignition switch for corrosion. Corrosion may bridge two contacts and make a complete circuit that won't disengage. Possible but not likely. I, personally, would start with replacing the solenoid.Also if you have a weak battery in the mower that will also cause that.You can rule out the starter,next check the solenoid to make sure it is not sticking.