1991 Ford f350 will not start using the key.

I've replaced the ignition switch and starter solenoid. Verified the linkage to the ignition switch is moving and actuating all positions. Jumped pins 32 and 32 together on the neutral safety switch. I can start the truck using a screwdriver to short the starter solenoid. It stays running and runs like normal. Im not sure what else to check. Any help would be appreciated.

 

The first thing I would do is get the wiring diagram for your truck Then start checking voltage should not be that hard to pin down.

 

Are you getting any voltage at the small wire that should' be connected to the upper little post on the starter solenoid? With key on "Start" there should be 12v at the little trigger wire. I've knocked that wire off before and suddenly the key wouldn't start the engine.

 

I get 12.7 volts to that little wire. Starting to think maybe the starter solenoid I purchased was faulty. I've tried jumping a wire straight from the battery to that same post and get nothing. But if I use a wrench to connect the 2 large post it starts right up.

 

That verifies it. Bad solenoid. When a good solenoid gets power to the S (start) terminal (when you turn the key all the way forward), it's supposed to internally connect the two main terminals (that you jumped together) and turns the starter.

 

Thank you for your help. Did some testing and the solenoid was not grounding through the case added a ground to the other small post and it starts great now.

 

sounds like the parts counter monkey gave you a glow plug relay instead of a starter relay.
the only difference between the two is starter relay is case grounded, glow plug relay is internal grounded through the other small terminal.