When inspecting a reciprocating engine, what is a common sign of combustion issues?

The condition of spark plugs is a key indicator of combustion issues in a reciprocating engine. Spark plugs play a crucial role in igniting the air-fuel mixture within the combustion chamber. When they are inspected, the appearance of the spark plugs can reveal a great deal about the engine's combustion process.

For example, if the spark plugs show signs of excessive carbon buildup, it may indicate that the engine is running too rich, meaning there is too much fuel in the air-fuel mixture. Conversely, if they are clean or white, this could suggest that the engine is running too lean, meaning there isn't enough fuel for proper combustion. Other conditions such as oil fouling, discoloration, or irregular wear patterns can also signal problems in the ignition system or combustion process. Therefore, evaluating the condition of the spark plugs provides valuable diagnostic insight into the overall health of the engine and the efficiency of the combustion process.