Cranking Circuit

The cranking circuit consists of the battery, starter motor, ignition switch, neutral start switch. If it becomes apparent that there is an electrical failure, refer to Starting System Check .

Starter Motor

Three different starter motors are used on these engines. The SD-255 is a straight drive starter with the pinion driven directly by the armature shaft. Each starter has pole pieces arranged around the armature that are energized by wound field coils. This type of starter is used on the 4.3L and 5.0L gasoline engines.

The PG-260 achieves gear reduction at a ratio of 5:1 through planetary gears. It's relatively small size and light weight and offers improved cranking performance and reduced current requirements for the 5.7L and 7.4L gasoline engines.

The 28-MT, used on the 6.5L diesel engine, is a gear reduction starter with an over running roller type clutch and enclosed shift lever. Enclosed shift lever cranking motors have the shift lever mechanism and the solenoid plunger enclosed in the drive housing, protecting them from exposure to dirt, icing conditions, and splash.

Solenoid windings are energized when the ignition switch or engine control switch is in the start position. The resulting plunger and shift lever movement causes the pinion to engage the engine flywheel ring gear, the solenoid main contacts to close, and cranking takes place. When the engine starts, the pinion over running clutch protects the armature from excessive speed until the ignition switch or engine control switch is released, at that time the plunger return spring causes the pinion to disengage. To prevent excessive overrunning, release the ignition switch or engine control switch from the crank position as soon as the engine starts.