2000 Expedition is killing the battery with ignition off

I had replaced a coil pack that fires one of my cylinders. The fuel line that is connected to the fuel injectors had to be removed to get to this particular one. I replaced the O-rings on the injectors, put everything back together including the vacuum lines I paid special attention too. The first test run, my brake pedal was very hard to press and the engine seemed to still be missing. The second run the brakes are fine, haven't seen a light yet, but still missing and the warning sound (ding-ding-ding) is sounding very rapidly after I turn ignition off and keys out. The battery is dead after a few hours.