Cleaning, Inspection and Testing

Starter Motor No Load Test:

SD-255 Brush Holder:

Armature Shaft And Drive Assembly:

Testing Field For Open:

Commutator End Bearing Installation:

Installing Retainer, Washer And Ring:

Drive End Housing Bearing:

Checking Pinion Clearance:

INSPECT
1. Clean all starter motor parts, but DO NOT USE GREASE DISSOLVING SOLVENTS FOR CLEANING THE OVERRUNNING CLUTCH, ARMATURE AND FIELD COILS, because solvents dissolve the grease packed in the clutch and damage armature and field coil insulation.
2. Test assembly drive action. The pinion should turn freely in the overrunning direction. check pinion teeth to see that they have not been chipped, cracked, or excessively worn. Replace assembly when necessary. Badly chipped pinion teeth can indicate chipped ring gear teeth, which should he replaced when necessary.
3. Check the drive assembly for slipping. Wrap the armature with a shop towel and clamp the armature in a vise. using a 12-point deep socket and torque wrench, put the socket on the pinion and turn counterclockwise. The clutch should not slip up to 68 N.m (50 lb. ft.) of torque. If it does, replace the drive assembly.
4. The roll type drive assembly requires no lubrication; however, the drive assembly should be wiped clean. Do not clean in any degreasing tank, or with grease dissolving solvents; this dissolves the lubricant in the drive mechanism.
5. Inspect armature commutator. When commutator is dirty, clean with 400 grit polishing cloth. When commutator is rough, the armature should be replaced. Do not undercut or turn commutators. Inspect the points where the armature conductors join the commutator bars to make sure they have a good connection. A burned commutator bar is usually evidence of a poor connection.
6. When test equipment is available:

SD-255 Brush Holder:

^ Check the armature for short circuits by placing on growler, and holding a hack saw blade over armature core while armature is rotated. If saw blade vibrates, armature is shortened. Clean between the commutator bars and recheck armature for short circuits. If saw blade still vibrates, replace the armature. Using a self-powered test lamp, place one lead on the field lead terminal and the other lead on the insulated brush, as shown in Figure above. If the lamp fails to light, the series coil is open and requires repair or replacement. This test should be made from each insulated brush to check brush and lead continuity.

Testing Solenoid Windings:

^ Using a self-powered test lamp, place one lead on the grounded brush holder and the other lead on either insulated brush. If the lamp lights, a grounded series coil is indicated and must be repaired or replaced.
7. Check Solenoid windings

Testing Field For Ground:

^ To check hold-in winding, connect an ammeter and switch in series with a 12-volt battery and the "S" terminal on the solenoid. Connect a voltmeter to the "S" terminal and to ground. Connect carbon pile across battery. Adjust the voltage to 10 volts and note the ammeter reading. Refer to Figure above.
^ SD-255 starter motor reading should be 10 to 20 amperes.
^ To check both windings, connect as for previous test. Ground the solenoid motor terminal "M." Adjust the voltage to 10 volts and note the ammeter readings. It should be 60 to 85 amperes for SD-2S5 motors.
^ Current draw readings that are over specifications indicate shorted turns or a ground in the solenoid windings. Replace the starter solenoid.
^ Current draw readings that are under specifications indicate excessive resistance. A zero reading indicated an open. Check/repair connections when possible, otherwise replace starter solenoid.
^ The starter solenoid is serviced as an assembly.