The glow plug system is a preheat system which rapidly warms the combustion chamber during a cold start. This initial heating allows the fuel to burn quicker, resulting in better cold driveability.
The earliest diesels required the driver to wait while the glow plugs worked; when the correct temperature was achieved, the engine could be started. Mitsubishi eliminated this long wait with what they call the Super Quick Glow System. By using both relays and a dropping resistor, the plugs are brought to their operating temperature almost instantly. The engine may be started within 5–10 seconds. Additionally, when the engine is running and the coolant temperature is below 130°F (55°C), the glow system will remain engaged, resulting in stable heat generation and reduced engine noise.
The glow plugs themselves are nothing more than resistance heating elements. Because they heat quickly, they consume heavy amounts of electricity. The high amperage required is conducted through a buss-bar (solid conductor) connected to each plug. It is important that the battery in a diesel vehicle be kept fully charged; otherwise the draw of the glow plugs combined with the draw of the starter will drain the battery.