During cold starts, which device heats the air entering the cylinder?

During cold starts, which device heats the air entering the cylinder?

• A. Spark Plug
• B. Glow Plug
• C. Heater Coil
• D. Auxiliary Heater

Answer: (B)

During cold starts the air inside the cylinder needs extra heat to ignite the fuel reliably, and that job is done by the glow plug. A glow plug is an electrical heating element placed in the combustion chamber; when energized during cranking in cold conditions, it heats the air (and chamber) to a temperature high enough for the fuel to ignite smoothly when it’s injected. The spark plug, by contrast, provides the ignition spark for gasoline engines and does not heat the incoming air. A heater coil isn’t used to preheat the cylinder air, and an auxiliary heater preheats the engine or cabin but doesn’t directly heat the air in the cylinder during start.

During cold starts the air inside the cylinder needs extra heat to ignite the fuel reliably, and that job is done by the glow plug. A glow plug is an electrical heating element placed in the combustion chamber; when energized during cranking in cold conditions, it heats the air (and chamber) to a temperature high enough for the fuel to ignite smoothly when it’s injected. The spark plug, by contrast, provides the ignition spark for gasoline engines and does not heat the incoming air. A heater coil isn’t used to preheat the cylinder air, and an auxiliary heater preheats the engine or cabin but doesn’t directly heat the air in the cylinder during start.