Glow Plugs

Glow plugs are small 6-volt heaters, powered by 12 volts to give rapid heating. Electronic controller operates glow plugs, which 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 different than the system for the LL4 (heavy duty emissions version). The LH6 system has the same glow plugs, glow plug controller and WAIT light. However, there is no temperature inhibit switch. Instead, the ECM, which receives temperature information from the coolant temperature sensor located in the water crossover of the engine, controls glow plug temperature inhibit.

The computer 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 computer controlled system, see G - DIESEL TESTS W/ CODES article in this section.