Ice bridging

A spark plug failure that occurs when starting a reciprocating engine in extremely cold weather. When a cylinder fires, the air/fuel mixture is converted into carbon dioxide and water vapor. The water vapor condenses on the spark plug electrodes and forms ice that bridges the electrode gap and prevents the plug firing until the ice is melted. This normally requires removing the spark plugs from the engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-15