Glow Plugs

Glow plugs are small 6-volt heaters powered by 12 volts to give rapid heating. The glow plugs are operated by the electronic controller and cycle on when ignition switch is turned to the "RUN" position, prior to starting the engine. The glow plugs remain pulsing a short time after engine starting, then automatically turn off.

The glow system for the LH6 (light duty emissions version) is somewhat different from the system for the LL4 (heavy duty emissions version). The LH6 system has the same glow plugs, glow plug controller and "WAIT" lamp. However, there is no temperature inhibit switch. Instead, glow plug temperature inhibit is controlled by the ECM which receives temperature information from the coolant temperature sensor, located in the water crossover of the engine.

The computer then transposes this temperature information into a voltage signal which it sends to the cold advance relay, ignition circuit and glow plug controller. The cold advance relay is located at the junction block in the engine compartment on the right side of the cowl. For diagnostic information on the computer controlled system, see appropriate article in COMPUTER ENGINE CONTROLS section.