Sabb 9-5 New Brake Pad Problems

I have just replaced the front brake pads on my 9-5 estate 2.2 TiD. All went well until i started the engine and found that the brake pedal went to the floor. I have bled the brakes and pumped the pedal many times and there is no change. Witht he engine off i have a solid brake pedal and brakes that work, with the engine on the pedal hits the floor and i have to pump it several times before the brakes work. What have i done wrong, no air was introduced when i fitted the pads. Help!!