I just replaced the solenoid for a 1984 f250 pickup, and after starting it I noticed a strange noise. I turned the key off, but it was still cranking. Is there any reason why a brand new solenoid should get stuck?
The circled wires are the ones I touched together. They both came off the solenoid.
I believe you are suggesting that the starter motor was still getting power after the ignition was turned off, so the starter was still turning by electrical power.
If this is the case, it can’t be the starter that is at fault, but must be either the solenoid or the ignition switch that is at fault.
You need to identify whether the thin wire on the solenoid that connects back to the ignition switch has 12V on it when this happens.
If there is 12V on the thin wire when the ignition is not in the start position, then the ignition key is faulty. If there is not 12V on the thin wire, then the solenoid is faulty.
I have repaired a vehicle where the ignition key was sticking a little in the starter position, rather than springing fully back into position 2. One other symptom was that that things like the radio were not working when the key stuck in the start position.
I repaired the same problem on a 1977 Ford van. The starter relay would not shut off. It burned out 2 starters and 2 relays. I used the wiring diagram to discover a connector on the top of the transmission. That connector had 2 wire pairs: one from the reversing lamp circuit and one pair from the neutral safety switch circuit. The wire insulation was crumbling and it caused 12 volts to enter the starter relay. I repaired the 4 wires and the problem is ... gone.
I finally got a hold of my mechanic and he said the solenoid is bad, so I got a new one and the problem seems to be gone.