What was found
ON CLIMB-OUT "AUTOFAIL" ILLUMINATED AND AIRCRAFT WOULD NOT PRESSURIZE IN "AUTOSTANDBY" OR "MANUAL" MODES. CONTINUED FLIGHT AT 10,000 WITH CABIN ALTITUDE OF 80 00. OUTFLOW VALVE SEEMED TO WORK NORMAL. REF 727 WDM 21-61-01 CHECKED FOR PWR AND GROUNDS AT CONNECTOR D1914, ALL CHECKS GOOD. L FWD PACK S/O VALVE P/N 398540-2-1 IS STUCK CLOSED. REMOVED AND REPLACED LT FWD PACK SHUTOFF VALVE PER MM 21-55-071-4. LT PACK NOT OPERATING CAUSED PRESS PROBLEM.