alright. Recently got a 78 Ford Bronco. 400
Whats going on. Sometimes it just won’t start. Sometimes I’ll try it, nothing. Leave it alone come back the next day fires right up. Or I’ll drive around all day no problems then go to leave and nothing. Looks like the previous owner was haveing the issue too. It has a new ignition relay. Battery. Voltage regulator. Starter. Ignition coil And ignition control module. I’ve looked through most wires. Don’t see anything loose. Idk what to try next. So what happens when it’s not starting. I turn the key and hear a kind of boing. I believe the ignition coil. And the brake light comes on. And that’s it. Put in the last part today. Fired right up. Drive around a bit. Went to the store and first turn nothing. Second then. It slowly fired up.

Idk cuz I’ve tried starting it from neutral not just park. And nothing. And if it where the switch the starter solenoid wouldn’t open right?

I’m still a bit confused on what you’re hearing when you turn the key to Run but it doesn’t start. If you hear the starter solenoid thump then your ignition and NSS circuits should be good. If it’s not cranking you’ve got an issue from the solenoid to the starter. If it’s cranking but not firing then it could be air, fuel, or spark.
Have you replaced the ignition switch on the column?

I had the same problem with my 5.8. I changed out the fuel pressure regulator and haven’t had a problem since.

So some times cranks right up, sometimes just the starter solenoid clicks (boing), and some time starts turning slowly?

I would suspect;

1 Starer Solenoid (rare to be bad if new but does happen)
2 Cable from solenoid to starter
3 Bad Starter Ground or engine to chassis grounds (check them all)
4 Bad starter. 1 or 2 bad windings will cause no rotation when you try to start then it’ll catch and drag or fire right up. Mine’s doing this now but it has to wait for my shoulder to finish healing for me to replace it