Incident
While climbing through 10,000 feet, the pilots noticed an abnormal engine sound and, seconds later, smelled smoke. They then observed smoke emanating from the windshield defroster ducts. In response, the pilots initiated an emergency descent. When power was reduced and the nose pitched down to start the descent, the smoke disappeared, but the engine began running rough.
Emergency Landing
The pilots executed an emergency landing to a non-towered airport. After taxiing to parking, they shut down the engine. Upon exiting the airplane, the pilots noted external fire damage to the engine cowling, but no active fire was present.
Examination
Postincident examination revealed that the fuel injector line to the Number 5 cylinder had fractured, and that the leaking fuel had ignited. Examination of the fuel line showed that it had been repaired, despite such repairs being prohibited by a manufacturer's service bulletin. The investigation was unable to determine when the repair was performed, or who performed it.