Yukon 2WD V8-393 6.5L DSL Turbo VIN S (1995)
Glow Plug: Description and Operation
Glow Plug Location
These are 6-volt heaters (operated at 12 volts) that turn "ON," when the ignition switch is turned to the run position, prior to starting the engine.
They remain pulsing for a short time after starting, then are turned "OFF."
A "GLOW PLUGS" lamp, on the instrument panel, provides information on starting conditions.
CIRCUIT OPERATION
A normal functioning system operates as follows:
A. Key "ON" engine not running and at room temperature.
1. Glow plugs "ON" for 4 to 6 seconds, then "OFF" for about 4.5 seconds.
2. Then cycle "ON" for about 1.0 second, "OFF" for out 3.0 seconds, and continue to cycle 1.0 "ON," 3.0 "OFF," for a total duration (including
the initial 4 to 6 seconds) of about 16 seconds.
B. If the engine is cranked during or after the above sequence, its possible the glow p1ugs will cycle "ON"/"OFF" after the engine control switch is
returned from the crank position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.
NOTE: All the times shown above are approximate, because they vary with initial engine temperature. The initial "ON" time and cycling
"ON"/OFF" times vary also, with system voltage and/or temperature. Lower temperatures cause longer duration of cycling.
GLOW PLUG AFTER START
The Powertrain Control Module (PCM) provides glow plug operation after starting a cold engine. This after start operation is initiated when the
ignition switch is returned to RUN, from the START position. While loss of this function may not cause a cold start complaint, it may result in
excessive white smoking and/or poor idle quality after start.
