Glow plugs are small heating elements used in diesel engines to help start the engine in cold conditions. They work by heating the air in the combustion chamber, making it easier for the diesel fuel to ignite. This is especially important because diesel engines rely on compression for ignition, which can be difficult in low temperatures. When the engine is turned on, the glow plugs heat up quickly, usually within a few seconds. Once the engine starts, the glow plugs may continue to operate for a short time to ensure smooth running. Proper functioning of glow plugs is essential for reliable engine performance, especially in colder climates.