1973 ElCamino after turning ignition key off, engine continues to run. Must disconnect battery cable to get it to stop.
it may be the switch on the steering column that is contoled by a rod from the ignition switch. plastic piece attached to the top of the column under the dash with a wide harness plugged into it. may be worn and the rod isn;t pulling the switch to the right position to kill the ignition.
back in the day, i would sometimes need to shut off the engine in reverse or drive before shifting to park & turning the key to off. run-on does happen.
The starter solenoid is an inexpensive item and can be the cause of what you have described.
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