Exhaust Emission Controls - 2.5L Diesel Engine Table Of Contents; Vacuum Hose Routing Schematic Description; Exhaust Gas Recirculation System Description And Operation; Typical Hose Routing - Jeep 200 Cherokee Service Manual

25 - 6 EMISSION CONTROL SYSTEM
EXHAUST EMISSION CONTROLS—2.5L DIESEL ENGINE
Description And Operation
VACUUM HOSE ROUTING SCHEMATIC
EXHAUST GAS RECIRCULATION (EGR)
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Diagnosis And Testing
EGR GAS FLOW TEST
Egr Solenoid Test
Description And Operation
VACUUM HOSE ROUTING SCHEMATIC
DESCRIPTION
Vacuum for the EGR system is supplied by the
internal engine mounted vacuum pump. Refer to
EGR System Operation for vacuum pump informa-
tion. Vacuum harness routing for emission related
components is displayed in (Fig. 1).
Fig. 1 Typical Hose Routing
1 – EGR VALVE
2 – TO VACUUM PUMP
3 – ELECTRIC VACUUM MODULATOR (EVM)
2000 JEEP CHEROKEE
TABLE OF CONTENTS
page
. . . . . . . 6
. . . . . . . . . . . . . . . . . . . . 7
. . . . . . . . . . . . . . . . . . . . 7
Removal And Installation
EGR VALVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
EGR TUBE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
ELECTRIC VACUUM MODULATOR (EVM) . . . . . . . 8
Specifications
Torque Chart—2.5L DIESEL . . . . . . . . . . . . . . 8
EXHAUST GAS RECIRCULATION (EGR)
SYSTEM
DESCRIPTION
The EGR system reduces oxides of nitrogen (NOx)
in the engine exhaust. This is accomplished by allow-
ing a predetermined amount of hot exhaust gas to
recirculate and dilute the incoming fuel/air mixture.
A malfunctioning EGR system can cause engine
stumble, sags or hesitation, rough idle, engine stall-
ing and poor driveability.
OPERATION
The system consists of:
• An EGR valve assembly. The valve is located on
the side of the intake manifold.
• An Electric Vacuum Modulator (EVM). The EVM
is sometimes referred to as the EGR control solenoid
or EGR duty cycle solenoid. The EVM controls the
"on time" of the EGR valve.
• The ECM operates the EVM. The ECM is
located inside the vehicle under the instrument
panel.
• An EGR tube connects a passage in the EGR
valve to the rear of the exhaust manifold.
• The vacuum pump supplies vacuum for the
EVM and the EGR valve. This pump also supplies
vacuum for operation of the power brake boosterb
and the heating and air conditioning system. The
pump is located internally in the front of the engine
block (Fig. 2) and is driven by the crankshaft gear.
• Vacuum lines and hoses connect the various
components.
When the ECM supplies a variable ground signal
to the EVM, EGR system operation starts to occur.
The ECM will monitor and determine when to supply
and remove this variable ground signal. This will
depend on inputs from the engine coolant tempera-
ture, throttle position and engine speed sensors.
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