1998 Ford Explorer cant get brake presure

Brakes problem
1998 Ford Explorer 4 cyl Four Wheel Drive Automatic

the piston in the front passenger caliper broke and broke the rotor, I replaced 3 calipers all 4 rotors and then bled the breaks, pedal was very spongey. So I replaced the vac booster and master cylinder, bled the brakes again and while the truck is off theres pressure inb the pedal but as soon as I start it the pedal goes to the floor again. Im at a loss what else can I do? I tried putting the key to on and pushing the pedal then releasing it to reset the brakes but it did nothing