No Brake Pressure

I Replaced the Front Rotors, brake pads, calipers(new not rebuild) & my Master cylinder (New Not rebuild). I bled the master cylinder on the bench prior to installing it. I then bled the entire brake system. I do not see any Air bubbles coming our of the bleeders. I have pressure on my brake pedal when the ingnition is in the off position. Once I put the ingnition in the on position I lose all pressure and the pedal goes to the floor. If the engine is running I need to pump the brake pedal to build up pressure so that the brakes will engage. I had this same pressure issue prior to changing the master cylinder. I thought that was bad that is why I replaced it. I did not have this issue when I installed new brake lines to the rear brakes. I also had to change the calipers rotors, pads to both back brakes ( 6 months ago)