As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING PREFLIGHT CHECK PILOT PULLED THE LT FIRE HANDLE TO CHECK THE SHUTTOFF VALVE OPERATION, WHEN HE PUSH BACK THE HANDLE THE VALVE STAYED CLOSED. SEVERAL TRIES WERE NECESSARY TO OPEN THE VALVE. DURING TROUBLESHOOTING, THE PROBLEM DID NOT REOCCUR BUT AFTER INVESTIGATION FOUND THAT THE RELAY CONTACT AND THE WIRE TERMINAL WAS CORRODED AND CONTACT A3 WAS FOUND BEARLY ATTACHED. RELAY, WIRE AND TERMINAL WAS REPLACED.