Truck Repair: Started engaging by iteself!!, battery cable, solenoid

Question
I have an 87 F150 V8.  I sometimes have a problem where the starter will keep try to start even after taking the key out of the ignition.  I have to disconnect the battery cable to stop it. If I connect the cable again, the starter will kick off again (without the key in.)  I've replaced the solenoid (several times.) After each replacement, it would work OK for a week or so and then start acting up again. I replaced the battery and it has been working great, until today. This time the truck started up, but the started seemed to be stuck again, causing the motor to sound terrible.  I had to disconnect the battery cable again.  And again, when I reconnected it the started kicked in.  Any ideas?

Thanks,
Joey

Answer
Hello Joey,

The small terminals on the solenoid are what activates the solenoid. Unhook them, and see if the solenoid still stays engaged.

If not, then the ignition switch would be my first suggestion.

If it still stays engaged, the solenoid is welding shut, but I will bet on the ignition switch.

Van