As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING RUN UP OF A NEWLY FACTORY REBUILT ENGINE, THE PROPELLER DID NOT CYCLE. IT WAS DISCOVERED THAT THE PLUG, BEHIND THE OIL SUPPLY TUBE HAD COME LOOSE AND WAS ALLOWING PRESSURIZED OIL FROM THE GOVERNOR TO FLOW BACK THROUGH THE CRANKSHAFT AND NOT ACTUATE THE PROP.