What was found
WHEN STARTING APU ON GROUND, NO LIGHT OFF, HOLDS AROUND 1.8 EGT AND LOW OIL PRESSURE LIGHT ILLUMINATED. WENT TO OFF WHEN LIGHT EXTINGUISHES, TRIED AGAIN. SAME RESULT. GROUNDED - YES. ACCOMPLISHED B737-900 FIM 49-90 TASK 803 LOW OIL PRESSURE SHUTDOWN. FOUND FAULT 49-91007 LOW OIL PRESSURE LIGHT. DURING VISUAL INSPECTION OF APU FOUND DAMAGE TO THE LOWER AFT AREA OF THE COMPRESSOR INLET PLENUM SEAL DISLODGED & SEAL RETAINER BENT. REMOVED AND REPLACED APU PER B737-900 AMM TASK 49-11-00-400-801 AND TASK CARD 78349010. LEAK AND OPS TEST GOOD.