1991 Ford F-150 ignition stays on

I have a 91 F150 4x4 auto trans 3 speed with overdrive, I believe it's a C6. I started it one day and when I went to shut it off, the key turned back to lock position, but motor did not quit. The dash lights stay on and the only way to shut off power is tto disconnect the battery. It has tilt wheel with cruise in the steering wheel cover. The only way I can restart it is to reconnect the battery, Put tilt in lowest position, hold key in start pos. And bang on top of column at tilt knuckle and it starts right up. At first I thought it was the key lock switch, so I pulled it and replaced it with a new one, and that made no difference. Can anyone tell me how to repair this, short of replacing the steering column?