What occurs around 1,500°F (816°C) with the spark plug?

The spark plug begins to glow around 1,500°F (816°C) due to the high temperatures generated during the combustion process within the engine. As the engine operates, the spark plug experiences extreme heat from the combustion of the air-fuel mixture. When the temperature reaches this critical point, typically, the metal components of the spark plug can start to emit visible light, which is indicative of its high temperature. This glowing is a result of the spark plug material becoming incandescent.

In addition, this phenomenon can indicate that the spark plug is functioning properly, as it is able to endure the high temperatures required for igniting the mixture in the combustion chamber. It's important for the spark plug to maintain its performance without failing or causing misfires at elevated temperatures. Understanding this behavior helps in diagnosing spark plug conditions and potential issues in engine performance.