Glow Plug Operation
In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Four glow plugs are used as an aid to starting.
Control of the instant start system glow plugs is accomplished by a glow plug control module and 4.7 volt glow plugs, requiring 2 seconds to heat up to 1, 000°C (1, 832°F). The temperature and the power consumption is controlled between the engine control module (ECM) and the glow plug control module within a wide range to suit the engine's pre-heating requirements. Each glow plug is energized individually. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability. A DTC will set if there is a glow plug system fault.
A normal functioning system operates as follows:
- Turn the ignition ON with the engine OFF and at room temperature.
- The glow plugs turn ON and heat up in 2 seconds and then are pulse-width modulated (PWM) for another 2 seconds.
- The glow plug wait lamp is ON for 1 second during cold start.
- The glow plug wait lamp may not illuminate during a warm engine start.
- If the engine is cranked during or after the above sequence, the glow plugs may cycle ON and OFF after the ignition switch is returned from the start position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.
The glow plug control module provides glow plug operation after starting a cold engine. This post-start operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.
The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.