What was found
APU FAILED ON START UP + IS LEAKING FUEL ONTO THE GROUND. THERE IS ALSO A STRONG SMELL OF FUEL IN THE CABIN ( APU INOP ). REMOVED FROM SERVICE. REMOVED AND REPLACED APU EXCITER TO SERVICEABLE FROM STOCK REF Q400 AMM 49-40-01-000-801 AND 49-40-01-400-801. OPS CHECK FAILED. REMOVED AND REPLACED IGNITER AND IGNITION LEAD TO SERVICEABLE FROM STOCK REF Q400 AMM 49-40-04-000-801, 49-40-07-000-801, 49-40-04-400-801, AND 49-40-07-400-801. OPS CHECK GOOD. CLEARS DMI NO FUEL LEAK FOUND AFTER OPS CHECK. AIRCRAFT RETURNED TO SERVICE.