Buick LeSabre 1965 Service Manual page 594

1 0 - 2 4 CRANKING SYSTEM
ELECTRICAL SYSTEMS
SECTION 10-D
CRANKING (STARTER) SYSTEM
CONTENTS OF SECTION 10-D
Paragraph Subject Page
10-23 Description of Cranking System . • 10-24
10-24 Operation of Cranking System. . . . 10-24
10-25 Cranking Motor and Solenoid
Switch 10-27
10-26 Trouble-Shooting Cranking
System 10-27
10-27 Periodic Inspection of
Cranking Motor 10-29
PcirciQrciph
Subject
10-28 Voltage Test of Cranking
System and Solenoid System
10-29 Amperage Test of Solenoid
and Pinion Clearance
Check.
10-30 Bench Test of Cranking Motor
10-31 Cranking Motor Repairs -
on Bench
Page
10-29
10-30
10-31
10-31
10-23 DESCRIPTION OF
CRANKING SYSTEM
In the Buick cranking system, the
e n g i n e is cranked by turning
the ignition switch to the ex-
treme clockwise position marked
"START". The "START" posi-
tion is spring loaded in such a
way that the switch returns to the
"ON" position when released.
The cranking system, shown sche-
matically in F i g u r e 10-24, is
composed of the following units:
*•• Battery and battery cables
(par. 10-11).
2. Cranking motor, including the
drive assembly which engages the
flywheel ring gear during crank-
ing operation (par. 10-25).
3. Cranking motor solenoid
switch, mounted on the cranking
motor, for shifting the drive as-
sembly and closing the motor
circuit (par. 10-25).
4. Ignition switch, which when in
the "START" position connects
a lead from the battery to the
solenoid switch, passing through
the neutral safety switch on the
way. During cranking the ignition
switch also connects the battery
directly to the ignition coil, there-
by by-passing the resistance wire
which normally s u p p l i e s the
ignition coil at a lower voltage.
5. Neutral safety switch (auto-
matic transmission cars only).
This switch is connected between
the ignition switch and the sole-
noid switch to prevent cranking of
the engine except when the trans-
mission control lever is in either
neutral (N) or park (P) position.
10-24 OPERATION OF
CRANKING SYSTEM
When the ignition switch is turned
fully clockwise to the "START"
position, a connection is made
from the battery terminal of the
ignition switch to the solenoid
terminal of the switch. From
here, a large wire carries the
current to a terminal on the sole-
noid switch of the cranking motor.
A neutral safety switch is located
in series in this wire. The trans-
mission control lever must be in
neutral (N) or park (P) position
so that the neutral safety switch
is also closed.
Closing of the ignition "START"
switch and the neutral safety
Switch permits battery current
to flow through the "pull-in" and
"hold-in" coils of the solenoid,
magnetizing the solenoid. The
plunger is pulled into the solenoid
so that it operates the shift lever
to move the drive pinion into
engagement with the flywheel ring
gear. The solenoid switch con-
tacts then closes after the drive
pinion is partially engaged with
the ring gear; this prevents any
possible gear clash. See Figure
10-24.
The closing of the solenoid switch
contacts causes the motor to
crank the engine and also cuts
out the "pull-in" coil of the so-
lenoid, the magnetic pull of the
"hold-in" being sufficient to hold
the pinion in mesh after the shift-
ing has been performed. This
reduces the current consumed by
the solenoid while the cranking
motor is operating. See Figure
10-24.
As soon as the engine starts run-
ning, the overrunning clutch starts
free-wheeling. This allows the
starter pinion to be driven by the
flywheel ring gear without causing
the armature speed to increase
greatly. (Because of the large
gear ratio between the pinion and
the ring gear, a seized overrun-
ning clutch will cause the arma-
ture to be driven at an excessive
speed which may c a u s e the
armature windings to be thrown).
As soon as the driver realizes
that the engine has started, he
releases the ignition key and a
spring in the ignition switch re-
turns it to the "ON" position.
This breaks the solenoid circuit
so that the solenoid is demag-
netized. A return spring then
actuates the shift lever to retract
the solenoid plunger, which per-
mits another spring to open the
solenoid s w i t c h contacts. The