What was found
AFTER STARTING BOTH ENGINES, AND PLACING BOTH PACKS IN AUTO, ISOL VALVE AUTO, ENGINE BLEED SWITCHES ON, APU BLEED OFF, THE RIGHT DUCT PRESSURE WAS 20 PSI AND THE LEFT WAS 8 PSI WITH ENGINES AT IDLE. PACKS AND ENGINE BLEED VALVES WERE CYCLED OFF, THEN BACK ON/AUTO WITH NO CHANGE. GROUNDED - YES. FOUND HIGH STAGE REGULATOR LEAKING FROM DIAPHRAGM. REMOVED AND REPLACED NO. 1 ENG. HIGH STAGE REGULATOR REF B737-900 AMM 36-11-07. INSTALLATION TEST OK. FOUND HIGH STAGE VALVE FAILED STEP 04.K. REMOVED AND REPLACED NO.1 ENG. HIGH STAGE VALVE REF. AMM 36-11-06. INSTALLATION TEST OK. REQUIRES ENG. BLEED AIR CROSSOVER OPERATIONAL TEST, REF. AMM 36-11-00-710-901.