What was found
PILOT REPORTED ON ENGINE START LOUD BANGING. NORMAL INDICATIONS IN FLIGHT DECK. ACFT GROUNDED. PERFORMED APU BITE TASK 49-61-00-700-801. FOUND FAULT CODE 49-94299. REPLACED STARTER GENERATOR FILTER ELEMENT IAW AMM 49-91-12. LEAK CHECKED GOOD FAULT CLEARED. ACCOMPLISHED APU SURGE CONTROL VALVE FUNCTIONAL TEST. NO FAULT FOUND. REPLACED SURGE CONTROL VALVE IAW AMM 49-52-41-000 801 AS PRECAUTION. ON OPERATING LT & RT PACKS THE LOUD NOISE AND VIBRATION FROM THE APU REPEATED. REPLACED APU IAW AMM 49-11-00-000-802. OPS CHECKED GOOD IAW AMM 49-11-00-710-801.