Starting System: Description and Operation
STARTING SYSTEMStarter Motor, Disassembled View:
The starting system consists of the following components:
^ starter motor
^ starter switch, part of the ignition switch
^ Digital Transmission Range (DTR) sensor (automatic transmission-equipped vehicles)
^ starter motor solenoid relay switch
^ starter solenoid
^ starter drive
7.3L Diesel Engine Starter Motor:
The starter motor:
^ is a wound field, gear reduction, 12 V DC motor.
^ has an integral starter solenoid.
^ has an overrunning clutch in the starter drive.
The starter motor solenoid relay switch:
^ controls current to the starter solenoid.
^ is engaged by the ignition switch.
^ connects the battery to the starter solenoid.
The digital transmission range (DTR) sensor on automatic transmission-equipped vehicles prevents starter motor engagement unless the transmission is in the NEUTRAL or PARK position.
The starter drive:
^ is operated by the starter solenoid.
^ engages the flywheel to turn the engine.
^ has an internal overrunning clutch to disengage the starter motor when the engine starts.
The starter solenoid:
^ is an electromagnet.
^ engages the starter drive to the flywheel.
^ when energized, contacts close, connecting the battery to the starter motor and causing the starter motor to turn the starter drive.
^ is kept in the energized condition by a hold-in winding until the starter switch is released.
Intake Air Heater Starting Aid System-Vehicles Built After 12/7/98
Air Intake Heater Element:
Air Intake Heater Relay Switch:
The intake air heater starting aid system improves cold weather starting and reduces white smoke and odor during cold weather starting and on extended idles.
The intake air heater starting aid system consists of the following:
^ Engine Oil Temperature (EOT) sensor
^ intake air heater relay switch
^ intake air heater element
^ Intake Air Temperature (IAT) sensor
^ Powertrain Control Module (PCM)
^ starter switch
Intake air heater starting aid system operation.
^ The system is activated by the PCM when the ambient air temperature is below 0°C (32°F), the engine oil temperature is below 55°C (131 °F) and the battery voltage is above 11.7 volts.
^ The intake air heater will stay on for 30 minutes as long as the engine is idling and the above conditions are met.
^ The intake air heating system will only activate once per "key on event". If the heater is activated and the vehicle is driven, the heater will not activate if the vehicle is taken back to idle.
^ The intake air is heated by using a heating element mounted into the compressor manifold.
^ The intake air heater relay switch, located next to the glow plug relay switch, supplies power to the intake air heater element.