Trying to get my brakes working. With truck running, brakes go almost to floor. With truck off, I can pump up brakes and have almost full pedal. If I pump up brakes with truck off and then start, the brakes go almost to the floor again.

Is this an indication of a bad power booster?

 

No it is not the booster. Sounds like you have air in the system but it is not the booster.

 

Thanks Lazy K, I installed speed bleeders (since I am doing the brakes as a one man job) and purged the fronts. Now I can lock it up. Need to go back and re-adjust shoes, left locks up but right doesn't, and do the rear.

The $12 speed bleeders were much cheaper than a booster, and the booster had to be ordered.