As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) WHEN REMOVAL OF THE REAR COVER TO ALLOW RE INDEXING OF THE FLIGHT IDLE FUEL FLOW IT WAS NOTED THE COIL SPRING HAD COME IN CONTACT WITH THE REAR COVER. THE RESULTING FRICTION HAD WORN THE COILS OF THE SPRING 50 PERCENT THROUGH. THE FCU WAS REMOVED AND SENT FOR REPAIR.