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TEST 65 – TEST STARTER MOTOR
CONDITIONS AFFECTING STARTER MOTOR
PERFORMANCE:
1. A binding or seizing condition in the starter motor bearings.
2. A shorted, open or grounded armature.
a. Shorted armature (wire insulation worn and
wires touching one another). Will be indicated
by low or no RPM.
b. Open armature (wire broken) will be indicated
by low or no RPM and excessive current draw.
c. Grounded armature (wire insulation worn and wire
touching armature lamination or shaft). Will be
indicated by excessive current draw or no RPM.
3. A defective starter motor switch.
4. Broken, damaged or weak magnets.
5. Starter drive dirty or binding.
DISCUSSION:
Test 62 verified that circuit board action is delivering
DC voltage to the starter contactor relay (SCR). Test
63 verified the operation of the SCR. Test 64 verified
the operation of the starter contactor (SC). Another
possible cause of an “engine won’t crank” problem is
a failure of the starter motor.
PROCEDURE:
The battery should have been checked prior to this
test and should be fully charged.
Set a VOM to measure DC voltage (12 VDC). Connect
the meter positive (+) test lead to the starter contactor
stud which has the small jumper wire connected to
the starter. Connect the common (-) test lead to the
starter motor frame.
Set the AUTO-OFF MANUAL Switch to its “MANUAL”
position and observe the meter. Meter should indicate
battery voltage, starter motor should operate and
engine should crank.
RESULTS:
1. If battery voltage is indicated on the meter but starter
motor did NOT operate, remove and bench test the
starter motor (see following test).
2. If battery voltage was indicated and the starter motor tried
to engage (pinion engaged), but engine did NOT crank,
check for mechanical binding of the engine or rotor.
If engine turns over slightly, go to Test 77 “Check and
Adjust Valves.”
Figure 10. Starter Motor (V-Twin Engines)
Figure 11. Starter Motor (Single Cylinder Engines)
CHECKING THE PINION:
When the starter motor is activated, the pinion gear
should move and engage the flywheel ring gear. If the
pinion does not move normally, inspect the pinion for
binding or sticking.
PINION
Figure 12. Check Pinion Gear Operation (V-Twin)
PART 4
DC CONTROL
SECTION 4.4
DIAGNOSTIC TESTS