We can help with the OEM set up of the wiring diagram on this vehicle.
However, if you put a fender mounted solenoid on it then I assume you used a starter with no internal solenoid. If not, then you have two solenoids and the fender mounted one is not needed.
What I would suggest is checking for voltage on both wires at the starter.
You should have twelve volts on the larger wire from the battery all the time. Then the other should only have twelve volts when you are cranking the engine.
If the starter continues to run, I suspect you have voltage there all the time which means the relay, or a solenoid are stuck.
Take a look at the picture below. Number 1 should be the battery feed and the smaller post on the bottom number 2 should be the trigger wire.
The way to tell this is to just bench test it by unhooking the connection for the trigger wire and use a screwdriver to jump the post from the battery to the trigger post. If the starter turns then that is the trigger post. If not, it is the other one. Clearly, I am not looking at your starter but that is normally the trigger post on most all Ford starters.
Please run through this and let us know what you find. Thanks
Images (Click to enlarge)
Wednesday, October 6th, 2021 AT 3:33 PM