Pontiac FIREBIRD 1972 Service Manual page 770

6E-8 1972 PONTIAC SERVICE MANUAL
%"
PIPE
COUPLING
Fig. 6E-8 Driving Retainer Off Snap Ring
CLEAN AND INSPECT
1.
Test overrunning clutch action. The pinion should
turn freely in the overrunning direction. Check pin-
ion teeth to see that they have not been chipped,
cracked, or excessively worn. Replace assembly if
necessary. Badly chipped pinion teeth may indicate
chipped teeth on the ring gear. This should be
checked under such conditions and replaced if neces-
sary.
2. Inspect brushes for wear. Replace if worn t o one-half
their original length. Check brush holders to see that
they are not deformed or bent, but will properly hold
brushes against the commutator.
3. Check fit of armature shaft in bushing of drive hous-
ing. Shaft should fit snugly in the bushing. If the
bushing is worn, it should be replaced.
4. The overrunning clutch, armature and fields should
not be cleaned in any degreasing tank, or with grease-
dissolving solvents, since these would dissolve the
lubricants in the clutch mechanism and would dam-
age the insulation in the armature and field coils. It
issuggested that all parts except the clutch be cleaned
with oleum spirits and a brush. The clutch can be
wiped with a clean cloth.
If the commutator is dirty, it may be cleaned with
No. 00 sandpaper. Never use emery cloth to clean
commutator.
SERVICE
ARMATURE
If the armature commutator is worn, dirty, out of round
or has high insulation, the armature should be put in a
lathe so the commutator can be turned down. The starter
motor commutator is of the molded type and should not
be undercut, since undercutting will reduce the bonding of
the molding material. When turning the molded com-
mutator, only a very light clean-up cut should be made.
The minimum diameter of the commutator after turning
should not be less than 1.650 inches. As a final step in this
procedure, the commutator should be sanded lightly with
No. 00 sandpaper to remove any burrs left as a result of
the undercutting procedure.
The armature should be checked for opens, short circuits
and grounds as follows:
1. Open
-
The most likely place for an open to occur is
at the commutator riser bars as a result of excessively
long cranking periods. Inspect the points where the
conductors are joined to the commutator bars for
loose connections. The poor connections cause arcing
and burning of the commutator bars as the starting
motor is used. If the bars are not too badly burned,
repair can often be effected by resoldering the leads
in the riser bars (using rosin flux), and turning down
the commutator in a lathe to remove the burned
material.
Short Circuit
-
Short circuits in the armature are
located by use of a growler. When the armature is
rotated in the growler with a steel grip such as a
hacksaw blade held above it, the blade will vibrate
above the area of the armature core in which the
short circuit is located. Shorts between bars are some-
times produced by brush dust or copper between the
bars. These shorts can be eleminated by cleaning out
the slots.
3. Ground
-
Grounds in the armature can be detected
by the use of a 1 10-volt test lamp and test probes. If
the lamp lights when one test probe is placed on the
commutator with the other probe on the core or shaft
(Fig. 6E-7), the armature is grounded. Grounds oc-
cur as 'a result of insulation failure which is often
brought about by overheating of the starting motor
produced by excessive long cranking periods or by
accumulation of brush dust between the commutator
bars and the steel commutator ring.