A CL65 IN CLB AT FL318 DECLARED AN EMER AND DIVERTED DUE TO LOSS OF #1 ENGINE OIL PRESSURE. IN FLT ENGINE SHUTDOWN.

Narrative

CLBING THRU 31800 FT MSL; THE #1 ENG OIL PRESSURE DROPPED TO 16 PSI (WELL IN THE RED). WE GOT AURAL 'ENGINE OIL' WARNING AND ASSOCIATED EICAS MESSAGES. IT WAS MY LEG; SO I HAD THE FO RUN THE CHKLISTS; AND WE SUBSEQUENTLY SHUT DOWN THE ENGINE. I DECLARED AN EMER SHORTLY AFTER STARTING A DSCNT BECAUSE WE COULD NOT MAINTAIN ALT. WE TURNED BACK TO ZZZ1 (OUR ORIGIN); AND REALIZED ZZZ2 WAS A MUCH BETTER CHOICE. WE CONFERRED WITH OUR DISPATCH; AND DIVERTED TO ZZZ2. SAFE LNDG ACCOMPLISHED AFTER COMPLETING ALL APPROPRIATE CHKLISTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THE ENGINE WAS A GENERAL ELECTRIC CF34-3B1 AND THE CAUSE OF THE LOW OIL PRESSURE BELOW THE RED LINE WAS A FAILED SCAVENGE PUMP. THE OIL PRESSURE TRANSMITTER WAS REPLACED; BUT THE REAL PROB WAS THE FAILED SCAVENGE PUMP. CALLBACK CONVERSATION WITH RPTR ACN 640053 REVEALED THE FOLLOWING INFO: THE RPTR WAS NOT CERTAIN OF THE FAILED COMPONENT BUT BELIEVES THE SCAVENGE PUMP WAS THE MAJOR CAUSE AND AN OIL CAP GASKET WAS ALSO REPLACED.