E6R System—Eight-Cylinder Engine—Typical; Egr Valve With Back-Pressure Sensor; Valve Opening Test; Valve Closing Test - Jeep J-10 Series 1982 Technical & Service Manual

1J-74 FUEL SYSTEMS
VACUUM DUMP VALVE
FORWARD
DELAY VALVE
ire
EGR CTO VALVE
THERMAL VACUUM
SWITCH (TVS)
EGR VALVE
CARBURATOR
90597
Fig. 1J-141 E6R System—Eight-Cylinder Engine—Typical
An integral back-pressure sensor is incorporated in
the EGR valve for all engines. Calibration is accom
plished by the selective use of different diaphragm
spring loads and flow control orifices. The unit combines
the functions of the EGR valve and back-pressure
sensor.
The flow (recirculation) of exhaust gas is controlled by
a movable pintle within the valve (fig. 1J-142). In the
relaxed position, spring pressure holds the pintle against
its seat, confining exhaust gases to the exhaust mani
fold. Carburetor ported vacuum is available at the
power diaphragm to force the pintle from its seat, but
this cannot occur while the air inlet valve in the power
diaphragm is open.
Exhaust gas exerts pressure (back-pressure) inside
the exhaust manifold whenever the engine is operating.
This pressure is conducted through the hollow pintle
stem into the control diaphragm chamber. If this pres
sure is great enough to overcome control spring pres
sure, the control diaphragm is moved against the air
inlet valve. Full vacuum is now applied to the power
diaphragm and the pintle moves off its seat. EGR action
now begins. If the back-pressure drops sufficiently, the
control diaphragm moves away from the air inlet valve,
the power diaphragm again relaxes and EGR action
stops.
When system vacuum remains constant, within the
range of the unit, recirculation is primarily a function of
the exhaust manifold back-pressure level. EGR oper
ation is then dependent on exhaust back-pressure and
exhaust gas is a fixed percentage of the incoming charge.
EGR Valvo Functional Tests
The mechanical condition of the exhaust system may
affect the operation of an EGR valve with a back
pressure sensor. Excessive back-pressure from exhaust
system restrictions may create driveability problems.
POWER DIAPHRAGM
CONTROL
DIAPHRAGM
VENT
VALVE
CONTROL
FLOW AREA
VACUUM
70421
Rg. 1J-142 EGR Valve with Back-Pressure Sensor
Refer to Chapter IK—Exhaust Systems for Restricted
Exhaust System Diagnosis. Leaks from the exhaust sys
tem may decrease back-pressure enough to prevent
proper EGR operation. This will increase undesirable
exhaust emissions. Visually inspect the exhaust system
if leaks are suspected.
Valve Opening Test
WARNING: Use extreme caution when engine is oper
ating. Do not stand in direct line with fan. Do not put
hands near pulleys, belts or fan. Do not wear loose
clothing.
With the engine at normal operating temperature and
at curb idle speed, rapidly open and close the throttle.
The throttle should be opened sufficiently for the engine
speed to attain 1500 rpm. A definite movement should
be observed in the EGR valve diaphragm. If the dia
phragm does not move, the probable causes are: faulty
vacuum hose to the EGR valve, defective EGR valve
diaphragm or defective back-pressure sensor dia
phragm. Inspect vacuum hoses for air leaks.
Valve Closing Test
With the engine at normal operating temperature and
at curb idle speed, manually depress the EGR valve
diaphragm. This should cause an immediate decrease in
engine speed, indicating that the EGR valve had been
properly preventing the flow of exhaust gas during idle.
If there is no change in engine rpm and the engine is
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