Fuel Injection System - Diesel: Operation

The glow plug system provides for fast chamber preheat if temperature at thermo switch is less than 122°F (50°C). Under these conditions, relay 1 is energized and glow plug indicator light is lit for a period of 3.5 seconds. Chamber preheat temperatures are raised to a level warm enough to permit starting of the vehicle. At temperatures above 122°F (50°C), relay 1 is inoperative and relay 2 is energized to provide stabilizing heat during starting.