Engine Fouling Spark Plugs

 
From: Orv
Sent: 7/11/2004 

On a recent flight instructing trip last month my students 162F started running extrememly rich and started missing due to carbon fouling the spark plugs.

We had flown for 6 hours with no problem. It started raining and as we were getting ready to head back to the hangar the engine started to miss. We decided to park it where were were and cover it up as it was missing quite severely.
After the rain quit we towed the helicopter back to the hangar and dried it out thinking that water had gotten into a connection causing an eratic reading.
 
We tried everything that we could think of including unplugging and replugging all connections, removing the computers and reversing them, ect. Several calls to the factory were not helpful in solving the problem. No matter what we tried the spark plugs would foul within 10 minutes of engine start.
 
It turned out that the water temp sensor had failed and was giving the FADEC computers a reading of -49deg. C. The computers then apparently ran the engine rich until it warmed up but the temp sensor never indicated a warm up so the rich condition continued resulting in the spark plugs fouling.

 
When the water temp sensor was unplugged the engine would continue to run without fouling the plugs. A new sensor was ordered and the engine ran fine after that. Rotorway personell stated that they had not seen this happen before so I thought that I would post this in case anyone experienced the same problem, it might save you a few days of frustration.
 
Orv 

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