Diesel engines rely on the heat of compression to initiate combustion. Cold engine start-ups may require extra engine cranking time to create the necessary heat to ignite the diesel fuel. One of the devices available to aid in cold starting the diesel engine are glow plugs. Six glow plugs are used to preheat the combustion chambers as an aid to starting .

The glow plugs are 10.5 volt heaters, operated at 12 volts, when the engine control switch is turned to the H position. This provides a pre-heat feature to the combustion chamber and improves cold engine start ups.

To initiate the glow plug operation, these starting procedures should be followed:

1. Turn the engine control switch to the H position. Wait a suitable amount of time, depending on atmospheric temperature, before cranking the engine.
2. Turn the engine control switch to the Start position, and release the switch when the engine starts.
3. If the engine does not start after 15 seconds of cranking, repeat steps 1 and 2 until the engine starts.

When the engine control switch is turned to the "H" position, current flows through the glow plug relay, and to the glow plugs, heating the glow plugs to 800°C (1472°F). When the ambient temperature is about 0°C (32°F), the glow plugs will take 20 to 25 seconds to heat.