[T2] Vacuum assist

[ka1dza]

Hi all,
I hope everyone is enjoying a great late Summer weekend.
I finally got all of the rubber brake hose, the master cylinder, and the old break fluid replaced. My son in law helped me bleed brakes so the pedal was up 5-6 inches with the engine not running. As soon as I start the engine, the pedal goes to the floor. Is the vacuum assist causing this? How do I fix it?

TIA!

Bob Pratt