DURING NORMAL START PROCEDURES, THE AIRPLANE ENGINE FAILED TO START. THE SOLO PILOT EXITED THE AIRPLANE WITHOUT PLACING THE PARKING ON OR CHOCKING THE AIRPLANE. HE ROTATED THE PROPELLER, AND THE ENGINE STARTED. THE AIRPLANE ACCELEARATED FORWARD. THE AIRPLANE MAINTAINED A STRAIGHT GROUND TRACK AND RAN INTO A HANGAR DOOR, PENETRATING IT. AN EXAMINATION OF THE IGNITION SWITCH REVEALED THAT IT HAD A MECHANICAL FAILURE. THE FAILURE PREVENTED THE MAGNETO FROM BEING GROUNDED EVEN THOUGH THE KEY WAS REMOVED OR THE SWITCH PLACED IN THE OFF POSITION.