As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE ENTERED THE COCKPIT, (KEROSENE EXHAUST) DURING CLIMB. THE AIRCRAFT RETURNED. THE FORWARD HEATER WAS SLOW TO LIGHT OFF. DURING RECENT FUEL NOZZLE CLEANING, THE O-RING SEAL THAT SEALS THE NOZZLE TO COMBUSTION TUBE WAS NOT INSTALLED, OR FELL OUT DURING REASSEMBLY. COMPLETING A PRESSURE DECAY TEST AFTER THIS TYPE OF MAINTENANCE WOULD PREVENT THIS TYPE OF INCIDENT.