PISTON 4649579 - Caterpillar

The possible causes of this failure are listed below:
The flywheel ring gear is damaged.
The shift lever is damaged.
The pinion drive is damaged.Test Step 1. CHECK THE FLYWHEEL RING GEAR
Remove the starting motor.
Visually inspect the flywheel ring gear. Expected Result:The ring gear should be in good condition. The ring gear teeth should not be worn.Results:
OK - The flywheel ring gear is correct. Go to test step 2.
NOT OK - The flywheel ring gear is incorrect.Repair: Repair the ring gear or replace the ring gear.STOPTest Step 2. TEST THE INTERNAL COMPONENTS OF THE STARTING MOTOR
Disassemble the starting motor. See Disassembly and Assembly.
Thoroughly clean the following items:
Starting motor case
Shift lever assembly
Armature shaft
Visually inspect the shift lever for damage. Expected Result:The shift lever is correct.Results:
OK - The shift lever is correct. Proceed to test step 3.
NOT OK - The shift lever is incorrect.Repair: Repair the shift lever or replace the shift lever.STOPTest Step 3. TEST THE OPERATION OF THE PINION
Apply ground to the starter by attaching a ground cable to the case of the starter.
Connect +Battery to the "Bat" terminal.
Place the starter on the bench. Apply the correct system voltage to the "S" terminal of the starter. Expected Result:The armature turns and the pinion gear extends properly.Results:
YES - The operation of the starter is correct.Repair: Replace the starter on the machine and test for proper operation.STOP
NO - The operation of the starter is not correct.Repair: Replace the pinion drive assembly.STOP