Hehkutulppa

Hehkutulppa, commonly known as a glow plug, is a heating device used in diesel engines. Its primary function is to assist in starting a cold engine. Diesel engines rely on compression ignition, meaning the fuel ignites when compressed to a sufficiently high temperature. In cold weather, the engine block and cylinders absorb heat, making it difficult for the compressed air to reach the autoignition temperature of diesel fuel.

A glow plug consists of a heating element, typically made of a resistive material like nichrome, encased in a metal sheath. When the engine is cold and the ignition is switched on, current flows through the heating element, causing it to heat up to a high temperature, often glowing red. This heat is transferred to the combustion chamber, preheating the air and making it easier for the diesel fuel to ignite when injected.

The glow plugs remain active for a short period after the engine starts to ensure smooth idling and prevent stalling, especially in very cold conditions. Modern diesel engines often use a glow plug control unit that manages the heating cycle automatically, optimizing performance and emissions. The duration and intensity of glow plug operation are determined by factors such as ambient temperature and engine coolant temperature. Issues with glow plugs can lead to difficulties in starting a diesel engine, rough idling, and increased emissions.