MECHS CROSS 2 SENSE LINES WHICH RENDERED ENG BLEED AIR INOP.

Narrative

THE ACFT WAS OPERATING WITH AN MEL PLACARD FOR #2 ENG BLEED AIR INOP. WHILE ENRTE TO RENO; BAD WX WAS ENCOUNTERED AND; PER PLACARD; ACFT DIVERTED TO SFO. DURING TROUBLESHOOTING OF THE #2 ENG PNEUMATIC SYS IT WAS DISCOVERED 2 SENSE LINES TO THE PRESSURE REGULATING SHUTOFF VALVE WERE CROSS-CONNECTED RENDERING ENG BLEED AIR INOP. PRIOR TO THIS INCIDENT ON FEB/93; DEN MAINT COMPETED A PYLON MODIFICATION REQUIRING REMOVAL/INSTALLATION OF THE #2 ENG. IT WAS DURING THIS MAINT THAT THE LINES WERE INADVERTENTLY INSTALLED INCORRECTLY. ALL WORK WAS COMPETED PER ACR ENG REMOVAL/INSTALL FORM AND CORRESPONDING ENG TRIM FORM. CURRENTLY; NEITHER WORK CARD INCLUDES A STEP TO OPERATE AFFECTED SYSTEMS (BLEED AIR; GENERATOR; HYD; DISTURBED DURING ENG REMOVAL. ACR IS IN THE PROCESS OF REVISING THE WORK CARDS TO INCLUDE SYS OPERATIONAL CHKS. IN ADDITION; MANUFACTURER; HAS ISSUED A SVC BULLETIN DATED MAR/87 FOR REPLACEMENT OF SENSE LINES TO PREVENT CROSS-CONNECTING. REVISIONS TO WORK CARDS; COMPLIANCE WITH THE SVC BULLETIN; AND INCREASED AWARENESS OF THIS PROB WILL PREVENT FUTURE OCCURRENCES OF CROSS CONNECTING THE SENSE LINES.