Start Fuel Nozzle
The start Fuel Nozzle pictured is not spraying fuel for start. Even if all your igniters are firing with no start fuel nozzles functioning, a start is questionable. In some cases you may get a light-off of main fuel vapors. In most cases of main fuel only there too much fuel and they will flood the igniters and they will not fire.
These nozzles have an extremely small orifice that can be plugged by small particles in the fuel or by ( more common ) coking around the nozzle. The coking is caused by fuel burning on the face of the nozzle.
The T-53 is designed so that when the start fuel solenoid closes air from the burner housing forces air through the start nozzle forcing out the remaining fuel so it does not burn on the face of the nozzle.
This is not a foolproof system. I recommend inspecting start fuel nozzles every 300 hours and flow checking them or sending them out to your engine shop and having them flow check them. Some of the nozzles can be cleaned or repaired by the engine shop. I do not recommend trying to clean them yourself,the orifice can be damaged.
Start Fuel nozzles when installed are directed at the igniter plugs for good starting. If the only igniter and only start fuel nozzle are on opposite sides of the engine, a good cool start is not likely, slow or hot starts harm internal engine parts.
Helicopter Maintenance Manager
Sacramento Metro Fire District