ENGINES runs up until I let off the start key
 

92 F150, 5.0 liter.After parts changes. New starter switch, distributor, ECM, TPS, Temperature sensor, solenoid,key cylinder. Engine is timed at BTDC. With start key pressed all the way down, engine starts and runs until I let off the key and it automatically dies. I manually operated the starter switch pressing the bar and releasing, but no start, so I know the steering actuator is out of play. Thinking it is on the battery side of the solenoid. Solenoid hooked up with 3 wires on starter side, one wire on battery side, s post used.

Many early vehicles have two circuits to the ignition system - one for Start and one for Run.

Here's a diagram I found that shows it. Seems like the problem would be with the Red/Lt Green wire from the ignition switch. Might be right at the connector to the ignition module on the distributor, or anywhere along the way.

Wild guess. The 4th diagram down is the one.

https://faceitsalon.com/92-f150-wiring-diagram/

All the truck's details need to be in your signature as this caption describes:

https://www.supermotors.net/getfile/...oorsticker.jpg
(phone app link)Are you saying this symptom didn't appear until after you changed the last part on this list?WHY was each part changed? Did each replacement pass the same test that the original failed? Do you still have the originals?What do you mean? Is it at TDC (0°)? Or is it at some angle BTDC? Did you follow the instructions on the VECI label?

https://www.supermotors.net/getfile/...um-93-5.8l.jpg
(phone app link)The starter didn't engage?It's a relay. The starter solenoid is ON the starter. WHICH wires are on each post? Read these captions:

https://www.supermotors.net/getfile/...rtwire9296.jpg
(phone app link)

https://www.supermotors.net/getfile/...yterminals.jpg
(phone app link)