What are glow plugs?

• A. Spark plugs
• B. Small electric heaters that heat the combustion space and help ignition until normal operating temperatures are reached
• C. They regulate air intake
• D. They are used to time fuel injection

Answer: (B)

Glow plugs are tiny electric heaters placed in the combustion space. Their job is to raise the temperature inside the cylinder so the fuel-air mixture can ignite more easily when starting, especially when the engine is cold. They heat during cranking and help ignition until the engine reaches normal operating temperature, after which the engine’s own heat is sufficient to keep combustion going. They are not spark plugs, which create a spark to ignite the mixture, nor do they regulate air intake or time fuel injection.