What is the phenomenon called when current travels down the outside of the spark plug due to moisture or dirt?

The phenomenon where current travels down the outside of the spark plug due to moisture or dirt is known as flashover. Flashover occurs when there is an insufficient insulation or gap for the electrical current to travel along the intended path, typically in a high-voltage environment. In the case of a spark plug, this can happen when contaminants such as moisture or dirt accumulate on the exterior, allowing the electrical current to find a shortcut to ground rather than jumping the designed gap inside the spark plug, which would ignite the air-fuel mixture in the engine as intended.

This process can lead to poor engine performance and starting issues because the spark plug can no longer create a proper spark at the necessary location. Understanding flashover is crucial for diagnosing ignition system problems and ensuring proper maintenance of small engine components. The other alternatives such as backfire, arc discharge, and electrolysis pertain to different electrical or combustion phenomena and do not specifically describe the issue of current escaping through the outside of the spark plug related to dirt and moisture.