Re: 91 Ford Probe Starter won't Stop?? :(
i mis-read this the first time i looked.
On your starter you will have 2 wires, one thick (main power feed), one thin(solenoid trigger)
As we don't like these things to run forever, get someone to drive the key.
Get them to start the car, whilst you get ready to pull the trigger wire off.
IF the starter stops after you pull the trigger wire, then its the ignition switch as suggested. If it continues to 'run' then its most likely the starter solenoid sticking and the started unit should be replaced.
You can also do this by simply running a 'test lead' direct from positive on the battery to the trigger terminal.