Had a fail to start after 5 seconds time so released the key it returned to run position but the starter kept turning engine over until I turned it to off. Tried it again and it started Thing everything was good but something wasn’t right cause it did it again later so I ran a wire to the starter to check when it drops voltage to the starter and it does as soon as engine starts but if you just hit start it stays on until you turn it off

 

First thing I would look at is the starter relay.

 

Switched out relay to rule it out that wasn’t it. I ran the wire to the starter solenoid to check when the power dropped off it. It stayed on after attempt to start the truck but as soon as the truck starts the power drops off. I’m wondering if the pcm is malfunctioning

 

What engine, build date?

 

Don't know the build date but its got the updated heads that don't blow the plugs out