As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) BOTH L/H & R/H FIREWALL SHUTOFF VALVES WOULD NOT COMPLETELY SHUTOFF FUEL TO ENGINE. ON TEARDOWN OF VALVE O-RINGS WERE FOUND TO BE NICKED.THE O-RINGS ARE NICKED EVERYTIME THE VALVE IS OPERATED. THE VALVES ARE OPERATED AS PART OF RUN-UP CHECKS.THE DESIGN OF THE VALVES IS SUCH THAT AS O-RING LUBRICATION IS WASHED AWAY BY REGULAR FLOW OF FUEL THE RING IS NICKED.