What was found
(CAN) PILOT REPORTED NR 2 ENGINE HARD TO START. SPARK PLUGS WERE REPLACED AND MAINTENANCE FOUND ALL MAGNETO SWITCHES IN THE ON POSITION, MAGS WERE TURNED OFF. IT IS ASSUMED THE SHUT-DOWN PROCEDURES WERE CUT SHORT. AIR CREWS WERE CAUTIONED ON DANGER OF LEAVING THE MAGNETOS LIVE. ENGINE WAS STARTED FOR ENGINE FUNCTIONAL CHECK AND WHEN THE LEFT MAG WAS SELECTED, THE ENGINE STOPPED. THE LEFT MAG WAS REPLACED, THE ENGINE RAN-UP SERVICEABLE AND THE AIRCRAFT WAS RETURNED TO SERVICE.