I am having issues with my brakes after replacing my front calipers. System is properly bled and it feels like a stiff pedal when the engine is off but when engine is on the pedal loses all pressure.
Brakes slightly engage torward end of pedal (last 1/2 inch). I’ve had multiple people look at it no one can figure it out. any help would be appreciated!

 

You should always include the Ranger year with questions

1999 3.0l
Why did you change the calipers?
Was there a brake issue prior to changing the calipers?

What you describe is air in the system, and no power assist engine off

The power booster should retain vacuum assist for 3 pedal presses after engine is shut off, then pedal will be hard to press that is normal
So test for that

If you changed master it needs to be adjusted to booster pushrod

If you have 4 wheel ABS it may have air in the 4WABS unit
If you have RABS it could have air in that unit
Which one do you have?