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10-8
TROUBLE DIAGNOSIS
ELECTRICAL SYSTEMS
(284)
10-9
CRANKING
SYSTEM-TROUBLE
DIAGNOSIS
a. No Cranking Action When Accelerator
Pedal is Pressed
1.
Make sure ignition switch is turned on.
On cars equipped with Dynaflow Drive, control
lever must be in neutral (N) or parking (P)
position.
2. Make quick check of battery and cables
(par. 10-7). If battery is low the solenoid
usually will produce a clattering noise, because
a nearly discharged battery will not sustain
the voltage required to hold solenoid plunger in
after solenoid switch has been closed.
3.
If
cranking motor operates but drive
pinion does not engage flywheel ring gear, drive
assembly is sticking on armature shaft. Re-
move motor to free up drive assembly.
4. If cranking motor does not operate, note
whether solenoid plunger is pulled into sole-
noid when control circuit is closed. Ordinarily
the plunger makes a loud click when it is pulled
in. If plunger is pulled in, control circuit is
okay and trouble is in solenoid switch or crank-
ing motor. Exert pressure against shift lever
to make sure plunger makes full travel and is
not sticking. The cranking motor must be re-
moved for repairs to switch or motor. (par 10-
39, 10-40, 10-41).
5. If plunger is not pulled into solenoid
when control circuit is closed, the control cir-
cuit is open, the relay is inoperative, or sole-
noid is at fault.
6. Use screwdriver to ground relay termi-
nal to which wire with green crossing tracers
is connected. If cranking motor then operates
when
control
circuit is closed, the circuit from
relay to ground through generator is open.
Ground the "A" terminal of generator with
jumper wire, and if cranking motor then op-
erates look for dirty commutator,
worn-
out
brushes, or open field coils in generator, and
for defective contacts in voltage and current
regulators.
7.
If
cranking motor does not operate with
relay terminal grounded (step 6) disconnect
wire having black parallel tracers from relay
and connect a 6-volt test lamp between this
wire and ground. If lamp lights when accele-
rator pedal is pressed, control circuit to relay
is okay and trouble is in relay or solenoid. Re-
move cranking motor for inspection and t
est
of
soleno id
switch, (par. 10-39).
8. If, in step 7, control circuit to relay was
found open (test lamp did not light) check for
loose connections or broken wires. Use jumper
wire to bridge across terminals of accelerator
vacuum switch and neutral safety switch (Dy-
naflow cars only) to check these units. If vac-
uum switch appears to be cause of open circuit,
make sure that throttle linkage is not sticking
and holding throttle partially open, which
would prevent switch from making contact.
Check accelerator vacuum switch timing (par.
10-32 or 10-33).
b. Cranking Speed Abnormally Low
Abnormally low cranking speed may be
caused by low battery or defective cables, de-
fective solenoid switch, defective cranking
mo-
tor, or an internal condition of
engine.
1.
Make quick check of battery. If low bat-
tery is indicated, test battery (par. 10-19 and
10-20). If defective cables are indicated, test
cables (par. 10-21).
2. If battery and cables are
.
okay, test
cranking motor and solenoid switch (par. 10-
37) .
3. If cranking motor and solenoid switch
test okay, the trouble is due to an internal con-
dition of engine. This may be due to use of en-
gine oil which is too heavy for prevailing tem-
peratures. NOTE: In cold w
eather
always de-
press clutch pedal when cranking engine to
avoid the load caused by stiff lubricant in trans-
mission. Car owners should be given this in-
struction. Tight pistons or bearings also im-
pose a heavy load on the cranking motor.
c.
Drive
Pin
ion Clash
After Starting
If
drive pinion clash occurs immediately fol-
lowing disengagement of pinion from flywheel
ring gear after engine has started running, try
starting engine by holding accelerator pedal
to the floor until engine has reached a speed
between 15 and 20 MPH. If clash occurs, check
the following points.
1.
Make quick check of battery (par. 10-
7). If low battery is indicated check electro-
lyte (par.
10-19)
and cranking voltage (par.
10-20). Replace low battery with fully charged
battery and test for clash again. A low battery
will cause drive pinion clash because the gen-
erator voltage, which builds up quickly to maxi-
mum, causes a momentary voltage between
generator and battery great enough to cause
solenoid switch
relay
to close again and operate
the solenoid.
2. If clash occurs with properly charged
battery, test closing voltage of generator cut-
. .
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