What was found
NR 2 ENGINE HAD NORMAL START, DURING START FOR NR 1 ENGINE NO N2 ROTATION WAS OBSERVED. NR 2 WAS SHUTDOWN THEN APPROXIMATELY 1 MIN. LATER NR 1 ENGINE COWLING BLEW OPEN. ALL BLEED VALVE SWITCHES WERE IN "AUTO" POSITION. INSPECTED ENGINE & FOUND AIR STARTER TURBINE CASE CRACKED FROM THE 6 O'CLOCK TO THE 12 O'CLOCK POSITION. INSPECTED ENTIRE ENGINE OF DAMAGE NONE FOUND. REPLACED AIR STARTER CARBON SEALS I.A.W. CFE 738 L.M.M. CH. 72-62-01. NONE WERE DEFORMED. REPLACED AIR STARTER, STARTER DUCT QAD SCREWS, STARTER CLAMP, & O-RINGS IAW F2000 MM. SERVICED STARTER IAW CH. 80-002. OPS. CK. GOOD. REPLACED ENGINE START VALVE IAW CH. 80-004. OPS CK. GOOD.