What was found
DURING A ROUTINE OIL CHANGE, UPON INSP OF THE "FINGER" SCREEN IN THE CRANKCASE OIL SUMP APPROX HALF OF WHAT APPEARED TO BE AN AN-960 WASHER WAS FOUND. NO PART LIKE THIS IS INTERNAL TO THIS MODEL OF ENGINE, BASED ON THE MFG IPC. FURTHER INVESTIGATION REVEALED THAT THIS PART CAME FROM THE ENGINE DRIVEN FUEL PUMP (PN LW-15473). WHEN THE PUMP WAS REMOVED, THE OTHER HALF OF THIS WASHER WAS FOUND. THE WASHER IS CONNECTED TO THE TOP PART OF THE SHAFT THAT IS ACTIVATED BY THE PUMP ARM AND ACTUATES THE FUEL PUMP DIAPHRAGM. LOSS OF THIS WASHER GREATLY REDUCED THE PUMPING ACTION AND SUBSEQUENTLY THE FUEL VOLUME. NO PROBLEMS WERE REPORTED IN ALL PHASES OF PREVIOUS FLIGHTS ALTHOUGH TYPICALLY AN AIRFRAME BOOST PUMP IS ON DURING TAKEOFF AND LANDING.