What was found
AIRCRAFT WAS GROUNDED: ON ALL 3 LEGS WHEN STARTING NUMBER 2 ENGINE WE GET A VERY STRONG FUEL AND EXHAUST ODOR IN THE CABIN AND FLIGHT DECK AS SOON AS FUEL IS INTRODUCED. THE ODOR CONTINUES THROUGH ENGINE START UNTIL RIGHT PACK IS TURNED ON, THEN THE ODOR DISSIPATES QUICKLY. WE NOTICED THAT AROUND 22% N2 THE ENGINE SEEMS TO STRUGGLETO GET TO 25% WHERE FUEL IS INTRODUCED, FOLLOWED BY THE STRONG ODOR. REMOVED AND REPLACED PACK FLOW CONTROL VALVE. PER AMM 21-51-00.