Good day Guys, I have a early 90's STX38 with a 12.5 kohler. I was mowing
and it started to run rough. I idled it down, and it just stopped running. I tried to start, had nothing, no click at the soleniod, no power. I jumped it with a battery charger, and it fired up. She wouldn't idle but would rev up and run at higher rpm's. When I disconnected the charger she would die. It will only stay running with the charger connected. Any ideas? Thanks.

A bad battery can cause this or even a bad connection between the battery posts and cable terminals. Apparently you have an after fire solenoid that requires power to operate, when you remove the jumper cables, with no power it shuts of the fuel supply and the engine dies.

Ok, thanks for your reply. So it must be obvious the coil and stator are functionally fine.
The system is using the charger as the power source. I'll check the battery. Thanks again.

It was the battery. I replaced it and it runs like a deere. Thanks.