My 87 f-150 starter keeps spinning even with ignition off have replaced the solenoid. Even tried several solenoids thinking I had bought a bad one ,Still same problem ! can anyone help?

 

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Are you talking about the "solenoid" up on the fender well, or the one on the starter? The one on the fender well is actually just a starter relay to pick up the actual solenoid on the starter. It's possible the contacts are welded in the solenoid on the starter. I'm assuming the starter circuit on your '87 is the same as what it is on my '92.

 

If its fuel injected, you must have a solenoid with a built in diode. The diode absorbs the residual voltage that the ECM applies to the wire that energizes the solenoid. If you have the right solenoid, the wire that energizes it obviously is shorted to some other wire in the harness that has above 10 volts, or, it could be an interrnal defect inside the ignition switch.
Phil