Buick LeSabre 1965 Service Manual page 597

ELECTRICAL SYSTEMS
CRANKING SYSTEM 1 0 - 2 7
shift lever then disengages the
drive pinion from the flywheel
ring gear. After the transmission
is shifted out of park or neutral,
the neutral safety switch will pre-
vent accidental engagement of the
drive pinion with the flywheel.
10-25 CRANKING
MOTOR AND
SOLENOID
SWITCH
The cranking motor assembly
consists of a motor, drive assem-
bly, shift l e v e r , and solenoid
switch. See Figure 10-26.
Cranking Motor, Drive
and Shift Lever
The cranking motor is an en-
closed shift lever type, having an
extruded frame, four poles and a
compound field. The drive end
housing is extended to enclose
the entire shift lever mechanism
and plunger to protect them from
road dirt, icing conditions, and
splash. The solenoid is flange
mounted onto the drive end hous-
ing and is sealed to the drive
housing by a sealing compound.
The shift lever return spring is
a compression type and is located
inside the solenoid case. A rubber
grommet assembled in the frame
around the field lead insulates it
from grounding and also prevents
dirt, water, and oil from entering
the motor.
The armature shaft is supported
at both ends in graphite bronze
bushings pressed into the com-
mutator end frame and the drive
housing. Neither of these bear-
ings require lubrication e x c e p t
during assembly. See Figure
10-26.
The four brushes are supported
by b r u s h holders mounted on
the field frame. Two opposing
brushes a r e connected to the
field coils. The field coils are
held in place by the pole shoes
which are attached to the field by
large screws. The field coils are
connected to an insulated con-
necting link in the field frame,
through which current is supplied
to the motor.
The drive assembly is mounted
on the motor armature shaft and
keyed to it by helical splines so
that it can be moved endwise on
the shaft by the solenoid operated
shift lever. It transmits cranking
torque to the flywheel ring gear,
but its overrunning clutch allows
the drive pinion to rotate freely
with reference to the armature
shaft when the engine begins to
operate, thus preventing the arm-
ature from being driven at ex-
cessive speed by the engine.
The drive assembly pinion is
moved into engagement with fly-
wheel ring gear by action of the
solenoid upon the shift lever,
which engages the shift collar of
drive assembly. The shift collar
moves the drive assembly by
pushing on the clutch spring,
which serves as a cushion in case
the pinion and gear teeth butt
instead of meshing. The helical
splines assist in obtaining proper
pinion engagement. The drive pin-
ion is pulled out of engagement,
after engine starts, by action of
the shift lever return spring. The
shift lever is connected to the
solenoid switch plunger by a roll
pin. See Figure 10-26.
The high torque cranking motor
has two parallel field coils con-
nected to the insulated brushes,
and two shunt field coils con-
nected to ground. The purpose
of t h i s design is to increase
starting torque. Heavier field and
armature windings help accom-
plish this. The additional shunt
field is required to control free
speed of the motor. See Fig-
ure 10-27.
b. Solenoid Switch
The solenoid s w i t c h not only
closes the circuit between the
battery and the cranking motor
to produce cranking action, but
it also operates the shift lever
to move the drive pinion into
engagement with the flywheel ring
gear.
The solenoid section of the switch
has a plunger and two windings,
the "pull-in" winding and the
"hold-in" winding. Together, they
provide sufficient magnetic at-
traction to pull the s o l e n o i d
plunger into the solenoid. The
plunger actuates the shift lever
and drive assembly and it also
closes the solenoid switch con-
tacts by pressing against a push
rod upon which a contact disk is
mounted between two coil springs.
One spring serves as a cushion
to insure firm contact of the disk
with two stationary contacts. The
other spring pushes the disk away
from the stationary contacts to
break the circuit when the sole-
noid is demagnetized after the
engine starts. One stationary con-
tact is connected to the battery
positive cable and the other is
connected to the motor windings
through a connector or bus bar.
See Figure 10-26.
Operation of solenoid switch, as
well as the entire cranking sys-
tem, is described in paragraph
10-23.
10-26 TROUBLE-SHOOTING
CRANKING SYSTEM
a. No Cranking Action
1. Make sure that control lever
is in neutral (N) or park (P)
position.
2. Make quick check of battery
and cables (par. 10-11). If battery
is low, the solenoid usually will
produce a clattering noise, be-
cause a nearly discharged battery