What was found
APU NO START AFTER LANDING, SHOWED MAINT MSG 49-1 1290. PER FIM49-52T808 TRIED TO START APU WITH EXTERNAL PNEUMATIC SOURCE. NO HELP. APU ONLY REACHING ABOUT 25% AND 450EGT BEFORE AUTO SHUT DOWN OCCURS. CYCLED APUC C-B S AMIS C-B S & INSPECTED APU CHECK VALVE. NO FINDINGS. FINAL APU START TRY-SAME AS BEFORE- AUTO SHUT DOWN-MAINT MSG 49-10630 AND FAULT CODE 49100400. FOR FURTHER TS DEFERRED PER MEL 4911A AND COMPLIED WITH. PERFORMED TASK 49-40 813. ITEM C(3) ITEM C. OPS CHECK OK. COULD NOT DUPLICATE PROBLEM.