What was found
AIRCRAFT WAS GNDED. AFTER DEPARTURE WHILE CLIMBING, THE NR 1 BLEED SYS FAILED, RESULTING IN A PRESSURIZATION ISSUE AS THE NR 2 BLEED AIR SYS WAS ALREADY ON MEL. DECLARED AN EMER & RETURNED WHERE THE ACFT LANDED SAFELY WITH NO FURTHER INCIDENT. FOUND A BLEED AIR LEAK COMING FROM THE STARTER DUCT IN THE NR 1 PYLON FWD SECTION & REPLACED THE STARTER DUCT IAW AMM 36-11-4 400. NO FAULTS WERE NOTED DURING AN OPERATIONAL CHECK OF THE SYS.