As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RECEIVED A FACTORY REBUILT ENGINE FROM TCM AND INSTALLED. DURING THE GROUND RUNS IT WAS DISCOVERED THAT THE LT MAGNETO WAS DEAD. FURTHER INSPECTION REVEALED THE PROBLEM TO BE IN THE MAGNETO ITSELF. A REPLACEMENT MAGNETO WAS ORDERED AND INSTALLED WHICH CHECKED OK.