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11-22
ENGINE ELECTRICAL
The solenoid is drawn into the engaged position
by the pull-in coil, and held inpositionby the hold-
in coil, while the ignition key is held in the extreme
right position, Fig. 11-29. The contact bar at the
end of the solenoid completes a direct circuit be
tweenthebattery and the starter motor, energizing
the starting motor.
The current consumption of the solenoid switch
should be 72-76 amperes at
10.0 volts for both
windings, and 18-20 amperes at 10 volts for the
hold-in winding alone.
36
Normal Cranking Motor
Maintenance
Lubrication
- -
Whenever the cranking motor is
disassembled for repair or service, place a few
drops of light engine oil on the oilless bushings in
the endbearings.Avoid excessive lubrication, since
this might cause lubricant to be forced out onto the
commutator where it would
gum
and cause
poor
commutation with a resulting inferior cranking
motor performance. Never oil commutator.
Inspection
--
Since there are no inspection win
dows in the extruded frame, the commutator end
frame should be removed periodically and the
brushes and commutator inspected. If the commu
tator is dirty, it may be cleaned with No. 00 sand
paper. NEVER USE EMERY CLOTH TO CLEAN
COMMUTATOR. If the commutator is rough, out-
of-round, or
has high mica it should be turned
down on a lathe and the mica
undercut. Worn brushes
should be replaced.
37
Checking Inoperative
Cranking Motor
If the cranking motor does not develop rated
torque and cranks the engine slowly or not at all,
check the battery, battery terminals and connec
tions, the ground cable, and the battery-to -cranking
motor cable, Corroded, frayed, or broken cables
should be replaced, and loose or dirty connections
corrected.
The overrunning clutch should withstand 50 to 60
foot
pounds torque without slipping. The pinion
should turn freely and smoothly in the overrunning
direction. The solenoid switch contacts should be
checked for burned condition, and the contact disc
and terminal studs replaced if necessary.
If the above are all in order, inspect the brushes
and commutator. The brushes should form a good
contact with the commutator and have the correct
spring tension. If there are burned bars in the com
mutator, it may indicate open circuited armature
coils which prevent proper cranking. Inspect the
Fig. 11-29 Starting Circuit
soldered connections at the commutator riser bars,
and resolder these connections and turn
down the
commutator as necessary.
Tight or dirty bearings will reduce armature
speed or prevent the armature from turning. A
worn bearing, bent shaft, or loose pole shoe will
allow the armature to drag, causing slow speed
or failure of the armature to rotate. Check for
these conditions. If the brushes, bearings, com
mutator, switch, etc., appear in good condition,
the battery and external circuit all right, and the
cranking motor still does not operate correctly,
remove the cranking motor for Bench Check as to
NO-LOAD and TORQUE tests,
38
Starter Motor Tests
1. NO-LOAD TEST
--
Connect the cranking
motor in series with a battery of the specified
voltage and an ammeter capable of indicating
several hundred amperes, If an R.P.M. Indicator
is available, read the armature R.P.M. also, Test
should indicate 95 amperes at 10.1 volts at approxi
mately 3500 R.P.M.
2. TORQUE TEST
--
Torque testing equipment,
if available, may be used to determine if the motor
will develop rated torque. A high current-carrying
variable resistance should be connected into the
circuit so the specified voltage at the cranking motor
may be obtained since a small variation in the volt
age will produce a marked difference in the torque
developed. The lock torque developed is 11 ths. ft.
at
460
amperes at 5.2 volts.
39
Interpretation of No-Load
and Torque Tests
1.
Low free
speed and high current draw with
low torque:
Neutral Switch
Acc
Starting Motor
a. Tight, dirty or worn bearings, bent shaft or
loose pole shoe screws,
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