A special spark plug is screwed into the combustion chamber of each cylinder. It consists of a housing with a heating rod pressed into it, formed by two spirals: heating and regulating. After applying voltage, the heating spiral in the rod heats up to a temperature of + 850°C for several seconds, while the current passing through the spark plug reaches 30 A. As the degree of heating increases, the resistance of the spiral also increases, which helps to reduce the current to 15 - 25 A. After the glow plug control lamp on the instrument panel goes out, the engine can be started.
The time spent on preheating the cylinders is no more than 10 s and is regulated by a special relay and the engine control module (ECM), which receives information about the current engine temperature through the coolant temperature sensor (ECT). Based on the analysis of the received data, the ECM controls the duration of the glow system operation and the operating current of the heating.
Note: On direct injection diesel engines, pre-heating is only necessary at temperatures below 0°C.