The high compression of a diesel engine causes the air temperature in the cylinder to become very hot. The compressed air temperature is usually hot enough – typically above 1,000°F (538°C) – to spontaneously ignite the fuel. This is called compression ignition or self-ignition. Compression ignition may NOT occur when the combustion chambers (cylinders) are cold; such is the case when starting a cold engine. The TITAN XD diesel engine incorporates a glow plug system to help start the engine by supplying additional heat to ignite the fuel when needed.
SYSTEM OVERVIEW
- Glow plugs provide a direct heat source to the combustion chamber helping the engine to start at cold ambient temperatures. The starter for diesel models is designed to NOT engage until the glow plugs have had sufficient time to warm up.
- The glow plug control module controls the timing and intensity of the glow plugs based on inputs such as engine speed, torque, coolant temperature, intake air temperature, and air pressure. These inputs are received via CAN communication from the ECM.
- Glow plugs reach operating temperatures above 1,832°F (1,000°C) in less than 2 seconds.
- Based on ambient temperatures and sensor inputs, the glow plugs may operate for up to 20 minutes after the engine has started. The extended glow plug operating time helps complete the combustion process and decreases noise output as the combustion chambers heat up.
DO NOT use starting aids (ether or other types of starting fluids or starting sprays) to help start the TITAN XD diesel engine. High glow plug temperatures can ignite ether or other starting aids and cause engine damage and/or personal injury.
GLOW PLUG SERVICE INFORMATION
- There is one glow plug per cylinder. Each glow plug is separately wired (has its own power circuit) to the glow plug control module.
- The glow plug electrical circuits are grounded through metal-to-metal contact at the tapered seat of the cylinder head.
- Glow plugs that are not properly grounded/tightened to the cylinder head may not operate correctly, causing engine performance issues and/or open circuit glow plug DTCs.
- Glow plugs do not use a sealing ring or washer. The body of a glow plug (when tightened to the cylinder head) relies on a tapered seat that mates with the taper in the cylinder head to seal the combustion chamber.
NOTE: DO NOT use anti-seize compound on the threads.
GLOW PLUG OPERATION
NOTE: The starter for diesel models is designed to NOT engage until the glow plugs have had sufficient time to warm up. During cold temperatures this could take up to 4 seconds.
Note: Always allow the Engine Warming – Keep Foot on Brake message to turn OFF before pushing the ignition switch the second time, or long engine cranking before start could occur.