TM9-4310-396-13
b.
Test Engine Starter Motor.
NOTE
To test engine starter motor, use a circuit tester capable of measuring volts and continuity (ohms).
(1) Motor armature coil ground test: use a circuit tester to check the insulation between commutator and shaft or
core. If continuity is detected, replace starter motor.
(2) Inspect surface of commutator. If corroded or pitted, clean with fine sandpaper. Replace starter motor if
commutator diameter measures less than 1.26 inches (32mm).
(3) Check motor armature shaft for wear, scarring, or discoloration from heat. If damage is found, replace
starter motor.
(4) Check the insulating material of commutator. If insulating material is not lower than commutator, correct
with hacksaw blade or undercutter. Insulating material should be .015 to .020 inches below commutator.
(5) Electrical coil open test: check electrical coil for disconnection and grounding. Check continuity between
terminals connecting electrical coil brushes. Continuity indicates the electrical coil is good. If not, replace
starter motor.
(6) Short-circuit test: check continuity between electrical coil case and electrical coil terminals. Continuity
indicates electrical coil is shorted and starter motor must be replaced.
NOTE
Do not remove electrical coil.
(7) Clean any carbon powder or rust that has been deposited in electrical coil by blowing out with dry
compressed air.
(8) Shunt coil continuity test: check continuity between C terminal (1, Figure 5-2) and relay- solenoid (4) case. If
no continuity is detected, replace relay-solenoid (4) whose shunt coil is open. Resistance of 1.13 0 (ohms)
should be detected.
(9) Series coil continuity test: check continuity between C terminal (1) and M terminal (2) of relay-solenoid (4)
case to insure continuity is detected. Series coil resistance is 0.33 n (ohms).
(10) Relay-solenoid contact test: Push plunger with your finger and check continuity between the M (2) and B (3)
terminals. If no continuity, relay-solenoid (4) is faulty and must be replaced.
5-7
