Dodge D150 1990 Service Manual page 708

+ FUEL SYSTEM 14 - 25
POSITIVE COILjs-ENGINE GROUND
TERMINAL STRAP
Fig. 18 Overdrive Solenoid
LOCK-UP TORQUE CONVERTOR
SOLENOIDS-SBEC OUTPUTS
O n v e h i c l e s equipped w i t h a n A-999 t r a n s m i s s i o n
(except California) t h e SBEC controls torque c o n -
v e r t e r lock-up t h r o u g h the Lock-up solenoid (Fig. 19).
Refer to Group 2 1 for solenoid i n f o r m a t i o n .
MODES OF OPERATION
A s i n p u t signals to t h e SBEC change, t h e SBEC
adjusts its response to the output devices. For exam-
ple, t h e SBEC m u s t calculate different injector pulse
w i d t h and i g n i t i o n t i m i n g for idle t h a n i t does for
wide open t h r o t t l e (WOT). There are several different
modes o f operation t h a t determine how t h e SBEC re-
sponds to the various i n p u t signals.
Modes of operation are of t w o different types.
O P E N L O O P a n d CLOSED LOOP.
D u r i n g O P E N LOOP modes the SBEC receives i n -
p u t signals a n d responds only according t o preset
SBEC p r o g r a m m i n g . I n p u t from the oxygen ( 0
2
) sen-
sor is not monitored d u r i n g O P E N L O O P modes.
Fig. 19 Lock-Up Solenoid
D u r i n g CLOSED L O O P modes t h e SBEC does
monitor the oxygen ( 0
2
) sensor i n p u t . T h i s i n p u t i n -
dicates t o the SBEC w h e t h e r o r not t h e calculated i n -
jector pulse w i d t h results i n t h e ideal air-fuel r a t i o of
14-7 parts a i r t o 1 p a r t fuel. B y m o n i t o r i n g the ex-
haust oxygen content t h r o u g h t h e 0
2
sensor, t h e
SBEC can "fine t u n e " t h e injector pulse w i d t h to
achieve o p t i m u m fuel economy combined w i t h low
emission engine performance.
The dual p o i n t fuel injection system has the follow-
i n g modes of operation:
• I g n i t i o n s w i t c h O N
• Engine start-up
• Engine w a r m - u p
• Cruise
• Acceleration
• Deceleration
• Wide Open T h r o t t l e
• I g n i t i o n s w i t c h OFF
The i g n i t i o n switch on, engine start-up (crank), en-
gine warm-up, acceleration, deceleration a n d wide
t h r o t t l e modes are O P E N L O O P modes. T h e cruise
mode, w i t h t h e e n g i n e a t o p e r a t i n g t e m p e r a t u r e
is a CLOSED L O O P mode.
Ignition Switch ON Mode
This is a n O P E N L O O P mode. W h e n the dual point
fuel injection System is activated by t h e i g n i t i o n
switch* the following actions occur:
• SBEC determines a m b i e n t atmospheric a i r pres-
sure from the M A P sensor i n p u t to determine basic
fuel strategy.
• The SBEC monitors t h e coolant temperature sen-
sor i n p u t . The SBEC modifies fuel strategy based on
t h i s input.
• The SBEC monitors t h r o t t l e body temperature sen-
sor i n p u t (5.2L and 5.9L engines only).
When the key is i n the O N position, the auto shut-
down (ASD) relay is not energized. Therefore battery