Armature Coil

Using an ohmmeter check that there is continuity between the segments of the commutator. See Fig 1. If any of the segments do not have continuity between them, replace the armature.
Check the commutator for ground. Using an ohmmeter, check that there is no continuity between the commutator and armature coil core. See Fig 1. If there is continuity, replace the armature.
If the surface is dirty or burnt, correct it with sandpaper (No.400) or a lathe.
Check for the commutator circuit runout. See Fig 2.
1. Place the commutator on V-blocks.
2. Using a dial indicator, measure the circle runout to ensure it is within specification. See STARTER SPECIFICATIONS . If the circle runout is greater than maximum, replace the armature.
.
Using vernier calipers, measure the commutator length. See Fig 3. If the length is greater than maximum, replace the armature.

Fig 1: Testing Commutator Ground & Continuity Between Segments

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 2: Measuring Commutator Runout

Fig 3: Measuring Commutator Length