What was found
AT 9000 FEET DURING APPROACH, THROTTLES BACK, NR 1 ENGINE START VALVE OPEN LIGHT ILLUMINATED FOR APPROXIMATELY 1 MINUTE, TURNED BOTH IGNITION SWITCHES FROM CONTINUOUS TO OFF, THEN BACK TO CONTINUOUS, MOVED BOTH THROTTLES UP, LIGHT EXTINGUISHED. ACFT GROUNDED. SUSPECT NR 1 ENG PNEUMATIC STARTER CONTROL VALVE DEFECTIVE. NR 1 ENG HAS BEEN REPLACED FOR UNRELATED BUSINESS REASONS. STARTER OPS CKS CARRIED OUT ON TC 78471001 UNDER, W/O 263885. EXISTING STARTER PRIOR TO ENGINE CHANGE TRANSFERRED TO DEFECT SHOP W/O 264541. NO HISTORY PREV 90 DAYS.