What was found
AT ENGINE SPIN UP, PNEUMATIC PRESS DROPPED OFF. ENGINE START ABORTED, APU DIED. ON GATE, NO MESSAGE ON CONTROLLER, CHIP DETECTORS CLEAN. APU STARTED, PNEU PRESSURE NORMAL, THEN SHUT OFF BY ITSELF, FOLLOWED BY APU SHUTDOWN. REPLACED APU CONTROLLER. REPLACED SURGE CONTROL VALVE PER MM. MOTORED NR 1 ENGINE AND LOAD WITH PACK. ALL SYSTEMS NORMAL.