Cold Weather Starts and Glow Plugs Glow Plug System Description Duramax 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. Eight glow plugs are used as an aid to starting. The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times all the times. The ECM 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 operation helps clean up excessive white smoke or poor idle quality after starting. Control of the instant start system, glow plugs is determine...