What was found
APU RUNNING BUT NO (ZERO) DUCT PRESSURE FOR ENGINE START. PREFORMED APU OPS CHECK IAW 49-11-00, APU FAULT ILLUMINATED @ 35 RPM. PREFORMED ECU BITE IAW FIM 49-11 FT 958. FAULTED LAST RUN START ABORTED AND SEE MANUAL. LRU SUMMARY, P2 SENSOR, DELTA P SENSOR, AND PT SENSOR. MINI FLAGS, 14,15,16,41,42,43,44,45,46,47,48, AND 120. R & R APU ECU IAW AMM 49-65-01.OPS CHECKED GOOD. R & R APU ECU IAW AMM 49-61-05. NO HELP STILL WOULD NOT START. PLACED ORIGINAL BACK IN AND BIT PER FIM 49-11 F/T 958. SUSPECT INLET PRESSURE SENSOR (P2) AND FLOW SENSING MODULE (PT, DELTA P) COMPLIED WITH INSPECTION MAGNETIC CHIP DETECTOR IAW AMM 49-27-04. NO DEFECTS NOTED. CHIP DETECTORS GOOD. REMOVED AND REPLACED APU IAW AMM 49-11-01 AND WO A49-999-00-01. APU OPS CHECK NORMAL, DUCT PRESSURE OPS CHECK NORMAL.