Pontiac Fiero 1988 Service Manual page 399

6D2-6 CRANKING SYSTEM
m' mo m m S T A R T E R MOTORS
DISASSEMBLY, T E S T AND R E A S S E M B L Y
(STARTER REMOVED FROM ENGINE)
N O - L O A D T E S T
AMMETER
C A R B O N
PILE
V O L T M E T E R
C D
SWITCH
SOLENOID
BAT.
I
S
CRANKING
MOTOR
3
JI
With the starter motor removed from the engine, the pinion
should be checked for freedom o f operation by turning it on the
screw shaft. The armature should be checked for freedom o f
rotation by prying the pinion with a screwdriver. I f the armature
does not turn freely, the motor should be disassembled i m -
mediately. However, i f the armature does rotate freely, the
motor should be given a no-load test before disassembly.
Make connections as shown. Close the switch and compare
the R P M , current, and voltage readings with the specifications
I f the specified current draw does not include
the solenoid, deduct from the ammeter reading the specified
current draw of the solenoid hold-in winding. Make disconnec-
tions only with the switch open. Use the test results as follows:
1. Rated current draw and no-load speed Indicates normal
condition of t i e starter motor.
2 .
Low
free speed and
h i g h
current draw indicates;
• Too much friction — tight, dirty, or worn bearings, bent
armature shaft allowing armature to drag.
• Shorted armature. This can be further checked on a
growler after disassembly.
® Grounded armature or fields. Check further after disas-
sembly.
3. Failure to operate with high current draw indicates:
© A direct ground in the terminal or fields.
® * * Frozen" bearings (this should have been determined by
turning the armature by hand).
4. Failure to operate with no current draw indicates:
• Open field circuit. This can be checked after disassembly
by inspecting internal connections and tracing circuit with a
test lamp.
• Open armature coils. Inspect the commutator for badly
burned bars after disassembly.
• Broken brush springs, worn brushes, high insulation be-
tween the commutator bars or other causes which would pre-
vent good contact between the brushes and commutator.
5. Low no-load speed and Sow current draw indicates:
o High internal resistance due to poor connections, defec-
tive leads, dirty commutator and causes listed under Number
4.
6.
High free speed and high current draw
usually
indicate
shorted fields. If shorted fields are suspected, replace the field
coil assembly. Also check for shorted armature, using a
growler.
_ _ _ 520042-6P
Fig. 8 0 2 Starter Motor Disassembly, Test and Reassembly 1 of 6