HELP! My pedal stays down when engine is running!

[bobfist]

I have everything new, brake booster, master cylinder , brakes etc.
When i apply vacuum to the brake booster the pedal won't come back up.
if i turn off the engine it comes back up!
Tested two master cylinders and check valves, whats wrong!?

[John_Kunkel]

Either the pedal pushrod is too long or the booster internal poppet valve or diaphragm return spring is faulty.

[bobfist]

the pedal works as i should if i remove the master cal