Approaching the top of the climb, the pilot of the Navajo
observed that the cylinder head temperature (CHT) for the left
engine was higher than normal. When the CHT started to exceed the
accepted company maximum of 400 degrees Fahrenheit, the pilot
enriched the mixture to attempt to control it. After reaching the
desired cruise altitude and speed, a vibration was felt through the
airframe. After confirming that the vibration was from the left
engine, the pilot decided that further troubleshooting was not
possible. He elected to shut down the left engine and feathered the
propeller. With concern for last light, a diversion to an alternate
aerodrome and successful single engine landing was carried out.
Maintenance investigation found that the left engine No. 6
cylinder fuel injection nozzle had become blocked. That cylinder
assembly had recently been changed and the engineer thought that a
small piece of ceramic might have been dislodged when the nozzle
and supply line was disturbed. The cylinder also had the single
cylinder head temperature probe for the left engine fitted to it
and would have registered the high temperature in this cylinder due
to the leaning effect of the blockage. The nozzle was cleaned and
the aircraft returned to service.