Starting System: Description
When the ignition switch is turned to the START position, the Delco-Remy starter solenoid windings are energized. This causes the solenoid plunger to move the shift lever, which engages the pinion with the engine flywheel ring gear. The movement of the plunger also closes the main solenoid contacts, applying battery voltage to the starter motor. See Fig 1.
When the engine starts, the pinion will overrun, protecting the armature from excessive speed and the flywheel from damage. When the ignition switch is released, the plunger return spring disengages the pinion.
On starters with the SD designation, used on 4.3L and 5.0L gasoline engines, the pinion is driven directly by the armature shaft. Wound field coils energize pole pieces that are arranged around the armature.
Starters with the PG designation, used on 5.7L and 7.4L gasoline engines, have a pinion that is driven by a 5:1 gear reduction system. These starters are easily identified by 3 Torx bolts that retain the solenoid. The PG starter should not be disassembled and is serviceable only by complete replacement.
Starters with the 28MT designation, used on diesel engines, have a pinion that is driven by a gear reduction system.