Starter Motor General Description

Three starter motors are used on these engines.

The SD-255 and SD-260 (4.3L and 5.0L engines) are both straight drive starters with the pinion driven directly by the armature shaft. Pole pieces are arranged around the armature that is energized by wound field coils.

The PG-260 (5.7L and 7.4L) achieves gear reduction at a ratio of 5:1 through planetary gears. Its relatively small size and light weight offers improved cranking performance and reduced current requirements.

The 28-MT, used on 6.5L diesel engine, is a gear reduction starter with an overturning roller type clutch and an 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 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 overrunning clutch protects the armature from excessive speed until the ignition switch is released, at which time the plunger return spring causes the pinion to disengage. To prevent excessive over-running, release the switch from the crank position as soon as the engine starts.

PG-260 model starters are serviced by replacement only. Other starting motors can be repaired.