What was found
RT ENG BLEED WILL NOT CLOSE WITH SWITCH OFF AND ISOLATION VALVE XSED. ALONG WITH ABOVE PROBLEM, WITH APU SUPPLYING AIR, ENG OFF, RT ENG BLEED OFF LIGHT EXTINGUISHES, APU BLEED VALVE LIGHT ILLUMINATES, DUCT PRESSURE DROPS, THEN APU BLEED VALVE LIGHT EXTINGUISHES. WHEN PRESSURE GETS TO ABOUT 5 PSI, APU BLD VALVE LIGHT FLASHES OFF AND ON, DUCT PRESSURE RISES AND RT ENG BLEED LIGHT ON. FOUND RIGHT ENG PRSOV OPENING WITH ANY BLEED SOURCE. REPLACED REVERSE FLOW CONTROL. NO HELP REPLACED RT PRSOV. BLEED OPERATES NORMAL.