What was found
LEFT DUCT PRESSURE AT IDLE ON GROUND, PACKS AUTO ANTI-ICE OFF WAS AT 10 PSI AT 40 PERCENT N1 ENGINE WENT TO 20 PSI. ACFT GROUNDED. PERFORMED FIM 36-10, TASK 804. DURING WRENCH CHECK OF PRSOV NOTED THAT PRSOV NOT SMOOTH IN MANUAL OPERATION. R & R PRSOV IAW AMM 36-11-04. REMOVED PN 3214552-6, SN 7662. LEAK CHECK GOOD BUT NO HELP WITH ORIGINAL WRITE UP. DURING FURTHER TROUBLESHOOTING FOUND LEAD CONTROL LINE TO HIGH STAGE VALVE BROKEN. R & R LEAD CONTROL SENSE LINE TO HIGH STAGE VALVE, PERFORMED OPS AND LEAK CHECK IAW AMM 36-11-06. VERIFICATION SUCCESSFUL. OK FOR SERVICE.