I should have gone back to bed this morning. I purchased an used Murray 17.5 HP with a 42" deck for my wife to help me. We have mowed with it for three times with no problem.
This morning, my wife wanted to mow. I tried to start the mower but could not get the key into the slot. We tried and tried. I finally removed a front panel and removed the old ignition switch. It has seven connectors. I called a mower repair. All they asked me was how many connectors did my switch have. They had one but they are 25 miles away. I called the local Tractor Supply Company. The girl that answered found a seven connector in stock.
I got it and installed it when I got home. As I was trying to put it back in the dashboard, I found a loose black wire. I saw a place in the plastic portion of the old connector without a wire. Being very hot and sweaty, I connected the black wire in the connector. I tried to start it up. The mower would almost start. Then it did. I chalked it up to a battery that will have to be replaced next Spring.
I turned the key to turn off the mower. It kept running. I got off the dead man's seat. It kept running. I removed the negative ground to the battery. It kept running. I removed the ignition switch and pulled the connector. It kept running.
I saw the wires going into the ignition switch were yellow. I had connected a black wire to the plastic connector and a yellow wire to the ignition switch. I reversed the wires and reconnected the ignition switch. I turned the key. It kept running. I removed the positive lead to the battery. You know what happened.
I decided to mow and run the gas out. I finished the mowing with a fourth of a tank left. I was going to let the gas run out but I could not let better enough alone. I had thought about pulling the boot off of the spark plug early in this process but that area was very hot. I thought I would give this another shot. I gently wiggled the boot without burning my fingers. I kept working at it until the park plug wire came out of the boot. IT QUIT RUNNING!
I know that I am stupid to pull the spark plug wire out but my question is, "Did I do something to the switch which prevented it from shutting off?" I may have mixed-up the yellow and black wires when putting the connector of the ignition switch. I need to fix this myself if possible.