System Operation - Jeep J-10 Series 1982 Technical & Service Manual

Two vacuum (4 in. Hg and 10 in. Hg) operated electric
switches, one mechanically operated electric switch, one
engine coolant operated switch (dual function) and one
air temperature operated switch are used to detect and
send engine operating data to the MCU. They detect the
following engine operating conditions.
• Cold Engine Start-up and operation
• Wide open throttle (WOT)
• Idle (closed throttle)
• Partial and deep throttle
Components
•Thermal Electric Switch (TES)—The TES is at
tached to the inside of the air cleaner to provide
either a ground circuit for the microprocessor to
indicate the necessity for a cold weather engine
start-up (when the air temperature is below the cali
brated value) or an open circuit to indicate normal
engine start-up (when the air temperature is above
the calibrated temperature).
•Coolant Temperature Switch—This dual function
switch is controlled by the engine coolant temper
ature and is integral with the intake manifold heater
control switch. When open, the switch indicates the
engine is cold (i.e., temperature less than 160°F or
71°C).
• 4 in. Hg Vacuum Switch—This switch is controlled
by carburetor ported vacuum and has a normally
closed (NC) electrical contact that indicates a closed
throttle condition. The switch is opened by 4 in. Hg
(13 kPa) vacuum level.
• 10 in. Hg Vacuum Switch—This switch is controlled
by manifold vacuum. When open, the switch in
dicates a deep throttle condition (i.e., non-cruise en
gine operating condition).
• Wide Open Throttle (WOT) Switch—This mechani
cally operated electrical switch (located at the base
of the carburetor) is controlled by throttle position
to indicate a wide open throttle condition.
NOTE: For the system to operate properly, all associ
ated componentsand relatedsystems must beintact and
operational This includes EGR valves, EGR related
componentry, correct ignition advance vacuum hose
routing, etc.
Engine RPM (Tach) Voltage
This voltage is supplied from the "tach" terminal on
the distributor. Until a voltage equivalent to a pre
determined rpm is received by the MCU, the system
remains in the Open Loop Mode of Operation. The result
is a fixed rich air/fuel mixture for engine starting
purposes.
Stepper Motor
The Stepper Motor is integral with the model BBD
carburetor. It controls the metering pins that vary the
FUEL SYSTEMS 1J-85
size of the idle and main air inlet orifices located in the
carburetor body. The motor moves the pins in and out of
the orifices in steps according to the control signal gen
erated by the MCU. The motor has a range of 100 steps,
but the normal operating area is mid-range (e.g., 40 to 60
steps).
When the metering pins are stepped in the direction of
the orifices, the air/fuel mixture becomes richer; when
stepped away from the orifices, the mixture becomes
leaner.
Dual Bed (TWC and COC) Catalytic Converter
This type converter has "downstream" air injection.
Whether air is injected "upstream" (i.e., directly into the
exhaust manifold) or "downstream" (i.e., into the con
verter) is a function of the MCU (microprocessor).
Refer to Exhaust Systems—Chapter IK for service
information concerning the dual bed (TWC and COC)
converter.
SYSTEM OPERATION
There are two primary modes of operation for both
the C4 and CEC Systems:
• open loop
• closed loop
Open Loop Mode of Operation
In general terms, each system will bein the open loop
mode of operation (or a variation of) whenever the en
gine operating conditions do not conform with the pro
grammed criteria for closed loop operation.
During open loop operation the air/fuel mixture is
maintained at a programmed ratio that is dependent on
the type of engineoperation involved. The oxygen sensor
data is not accepted by either system microprocessor
during this mode of operation. The following conditions
involve open loop operation (fig. 1J-154).
• Engine Start-Up
• Coolant or Air Temperature Too Low
• Oxygen Sensor Temperature Too Low
• Engine at Idle Speed
• Wide Open Throttle (WOT)
• Battery Voltage Too Low
Closed Loop Mode of Operation
When all input data conforms with the programmed
criteria for closed loop operation, the oxygen content
output voltage from theoxygen sensor isaccepted by the
microprocessor. This results in an air/fuel mixture that
will be optimum for the current engine operating condi
tion and also will correct any pre-existing too "lean" or
too "rich" mixture condition (fig. 1J-154).
NOTE: A high oxygen content in the exhaust gas in
dicates a "lean" air/fuel mixture. A low oxygen content
indicates a "rich" air/fuel mixture. The optimum air/
fuel mixture ratio is U.7:l.