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8D - 6
IGNITION SYSTEMS
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propriate retainers. F a i l u r e to route the cables prop-
erly can cause the radio t o reproduce i g n i t i o n noise,
cross i g n i t i o n o f the spark plugs or short c i r c u i t the
cables t o ground.
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 r e m o v i n g t h e spark p l u g spray com-
pressed a i r around t h e spark p l u g hole and the area
around the spark p l u g .
(2) Remove the 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 to Spark
P l u g C o n d i t i o n i n t h i s section.
Spark Plug Gap Adjustment
(1) Check t h e spark p l u g gap w i t h a gap gauge. I f
the gap i s n o t correct, adjust i t by bending t h e
ground electrode (Fig. 7).
Spark Plug Installation
(1) S t a r t the spark p l u g into the cylinder head b y
h a n d t o avoid cross t h r e a d i n g .
(2) T i g h t e n t h e spark plugs t o 41 N*m (30 ft-lbs)
torque.
(3) I n s t a l l spark p l u g cables over spark plugs.
SINGLE BOARD ENGINE CONTROLLER (SBEC)
The Single Board Engine Controller (SBEC) is a
d i g i t a l computer c o n t a i n i n g a microprocessor. The
SBEC controls t h e i g n i t i o n system, fuel injection,
speed control, alternator output, and other vehicle
operations based upon inputs i t receives from various
sensors and switches.
The SBEC controls t h e ground p a t h for the i g n i t i o n
coil and fuel injectors. The SBEC (Fig. 14) supplies
b a t t e r y power to t h e i g n i t i o n coil, fuel injectors, fuel
p u m p , and oxygen sensor h e a t i n g element t h r o u g h
the auto shutdown (ASD) relay. Refer t o " A u t o Shut-
down (ASD)
Relay" i n t h i s section for relay opera-
t i o n .
B y s w i t c h i n g the ground p a t h for the i g n i t i o n coil
on and off t h e SBEC adjusts i g n i t i o n t i m i n g to meet
changing engine conditions.
The amount of electronic spark advance provided
by t h e SBEC is determined b y four i n p u t factors,
coolant temperature, engine r p m , t h r o t t l e position
and
available
m a n i f o l d
vacuum.
D u r i n g
engine
cranking/start-up, t h e SBEC advances t h e i g n i t i o n
t i m i n g a set amount.
Based o n inputs t h a t i t receives, t h e SBEC also
controls idle speed a n d evaporative canister
purge
operation. T h e SBEC adjusts t h e alternator charge
rate t h r o u g h control o f the alternator field.
Refer t o Group 14, F u e l Systems, for f u r t h e r infor-
m a t i o n on the SBEC and fuel injection systems.
Fig. 14 Single Module Engine Controller (SBEC)
HALL EFFECT PICK-UP ASSEMBLY
The d i s t r i b u t o r pick-up is a H a l l Effect device (Fig.
15). The pick-up supplies engine position and r p m i n -
f o r m a t i o n t o t h e SBEC.
Fig. 15 Hall Effect Distributor 3.9L Engine
A shutter (sometimes referred to as a n i n t e r r u p t e r )
is attached to t h e distributor shaft (Fig. 16). T h e
s h u t t e r contains one blade per engine cylinder. A
s w i t c h plate is mounted to t h e d i s t r i b u t o r housing
above the shutter. The switch plate contains the dis-
t r i b u t o r pick-up (a H a l l Effect device and magnet)
t h r o u g h w h i c h the shutter blades rotate. A s the shut-
t e r blades pass t h r o u g h the pick-up, t h e y i n t e r r u p t
t h e magnetic field. The H a l l effect device i n the pick-
u p senses t h e change i n t h e magnetic
field a n d
switches o n and off (which creates pulses), generat-
i n g the i n p u t signal to the SBEC. T h e SBEC calcu-
lates engine speed t h r o u g h t h e number o f pulses
generated.
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