What was found
(CAN) DURING THE PREPARATION FOR A FLIGHT, AFTER THE BLEED SELECTION WAS ON, LOW POWER, DISC OR START/FEATHER, IMMEDIATELY A BAD ODOR WAS NOTICEABLE OUT OF THE AIR CONDITION. THE ENGINE WAS STOPPED AND THE ODOR CEASES SLOWLY AND NO ODOR WAS NOTICEABLE WITH THE APU. AFTER THE RESTART OF THE AFFECTED ENGINE AND THE BLEED SELECTION WAS ON AGAIN, A STRONG SMELL WAS IMMEDIATELY DETECTED. THE TROUBLESHOOTING IS ONGOING.