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8D - 12
IGNITION SYSTEMS
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SPARK PLUG SERVICE
SPARK PLUG
REMOVAL
Remove t h e spark p l u g cable b y grasping a t t h e
spark p l u g boot t u r n i n g the boot 1/2 t u r n and p u l l i n g
s t r a i g h t back i n a steady motion.
(1) P r i o r t o removing t h e spark p l u g spray com-
pressed a i r around the spark p l u g hole and the area
around t h e spark plug.
(2) Remove t h e spark p l u g u s i n g a q u a l i t y socket
w i t h a rubber or foam insert.
(3) Inspect the spark p l u g condition. Refer t o Spark
P l u g Condition i n t h e Component Identification sec-
t i o n o f t h i s group.
INSPECTION
Inspect t h e spark plugs for t h e following items.
Clean or replace i f necessary.
(1) Cracked or damaged threads or insulator.
(2) W o r n electrodes.
(3) Damaged or w o r n gasket.
(4) Condition of b u r n t electrode a n d amount o f car-
bon deposit.
Refer t o t h e General I n f o r m a t i o n section o f t h i s
group for i n f o r m a t i o n regarding spark p l u g condi-
t i o n .
SPARK PLUG GAP
ADJUSTMENT
(1) Check the spark p l u g gap w i t h a gap gauge. I f
the gap is not correct, adjust i t b y bending t h e
ground electrode.
SPARKPLUG
INSTALLATION
(1) S t a r t t h e spark p l u g i n t o t h e cylinder head b y
h a n d to avoid cross threading.
(2) T i g h t e n t h e spark plugs t o 4 1 N*m (30 ft-lbs)
torque.
(3) I n s t a l l spark p l u g cables over spark plugs.
IDLE RPM TEST
WARNING:
APPLY
PARKING
BRAKE
AND/OR
BLOCK
WHEELS
BEFORE PERFORMING
IDLE
CHECK OR ADJUSTMENT, OR ANY TESTS WITH A
RUNNING ENGINE.
E n g i n e i d l e set R P M s h o u l d b e t e s t e d a n d r e -
c o r d e d w h e n t h e v e h i c l e i s first b r o u g h t i n t o
shop for testing. This w i l l assist i n diagnosing com-
plaints o f engine stalling, creeping, and h a r d s h i f t i n g
on vehicles equipped w i t h automatic transmissions.
T e s t p r o c e d u r e s a r e a s follows:
(1) Connect red lead o f test tachometer u n i t to neg-
ative p r i m a r y t e r m i n a l of coil a n d black lead t o a
good ground.
(2) T u r n selector switch to t h e appropriate cylinder
position o f engine being tested.
(3) T u r n tachometer r p m s w i t c h t o 1,000 r p m posi-
t i o n .
(4) W i t h engine a t n o r m a l operating temperature,
m o m e n t a r i l y open t h e t h r o t t l e and release i t t o en-
sure there is no b i n d i n t h e l i n k a g e a n d t h a t t h e
t h r o t t l e lever is against i t s stop.
(5) Note engine r p m . Refer to Vehicle Emission
Control I n f o r m a t i o n ( V E C I ) label for correct engine
idle r p m . I f n o t w i t h i n specification, Refer t o " O n
Board Diagnostics" section o f Group 14, F u e l System
for t h r o t t l e body m i n i m u m air-flow check procedure.
IGNITION TIMING PROCEDURE
Proper i g n i t i o n t i m i n g i s required t o obtain opti-
m u m engine performance. T h e d i s t r i b u t o r m u s t be
correctly indexed t o provide correct i n i t i a l i g n i t i o n
t i m i n g .
WARNING:
APPLY
PARKING
BRAKE
AND/OR
BLOCK WHEELS BEFORE CHECKING IGNITION
TIMING.
(1) Set t h e gearshift selector i n p a r k o r n e u t r a l and
apply t h e p a r k i n g brake. A l l l i g h t s a n d accessories
m u s t be off.
(2) U s i n g a magnetic t i m i n g u n i t , i n s e r t the p i c k u p
probe into t h e open receptacle i n f r o n t o f the t i m i n g
scale (Fig. 3). I f a magnetic t i m i n g u n i t is not a v a i l -
able, use a conventional power t i m i n g l i g h t con-
nected to t h e n u m b e r one cylinder spark p l u g w i r e .
Fig. 3 Timing Marks
D o n o t p u n c t u r e c a b l e s , b o o t s o r n i p p l e s w i t h
t e s t p r o b e s . A l w a y s u s e p r o p e r a d a p t e r s . P u n c -
t u r i n g t h e s p a r k p l u g c a b l e s w i t h a p r o b e
w i l l
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