What was found
FL310, CABIN CLIMB GAUGE READS PLUS 500 SHORTLY AFTER FLOW LIGHT. CABIN PRESS READS 5.500 FT. NORMAL CABIN STARTING A SLOW CLIMB THAT COULD NOT BE STOPPED, EVEN WITH CONTROLLER MANUAL/FULL CLOSED. AT ABOUT 8800 FT CABIN ALT STOPPED EMERGENCY DESCENT. COMPLIED WITH ALL QRH ITEMS. DIVERTED TO ACY. CABIN NEVER RECOVERED. CABIN ALT NEVER ABOVE 15K. ALL MASKS DROPPED AS REQ 39329-2 DECAY CHECK REQUIRED REF TO TIME 39329-3, 39329-3. FOUND AFT SAFETY VALVE TO BE OPENING AT 7.6 PSI VALVE CHECKED BAD .39330-2 POST MAINTENANCE TEST FLIGHT DUE FOR PRESSURIZATION. AFT CABIN SAFETY VALVE WAS FOUND BAD AND CHANGED AND CABIN DECAY CHECKED ALSO PERFORMED AUTO PRESSURIZATION CHECK. (M)