Jeep Cherokee 2000 Service Manual - page 1943
If there is no leak the pump will quit. If there is a
leak, the test is terminated at the end of the test
mode.
If there is no leak, the purge monitor is run. If the
cycle rate increases due to the flow through the
purge system, the test is passed and the diagnostic is
complete.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
A typical system schematic is shown in (Fig. 3).
CRANKCASE VENTILATION SYSTEM
DESCRIPTION
All 2.5L 4–cylinder and 4.0L 6–cylinder engines
are equipped with a Closed Crankcase Ventilation
(CCV) system (Fig. 4) or (Fig. 5).
OPERATION
The CCV system performs the same function as a
conventional PCV system, but does not use a vacuum
controlled valve.
On 4.0L 6 cylinder engines, a molded vacuum tube
connects manifold vacuum to top of cylinder head
(valve) cover at dash panel end. The vacuum fitting
contains a fixed orifice of a calibrated size. It meters
the amount of crankcase vapors drawn out of the
engine.
On 2.5L 4 cylinder engines, a fitting on drivers
side of cylinder head (valve) cover contains the
metered orifice. It is connected to manifold vacuum.
A fresh air supply hose from the air cleaner is con-
nected to front of cylinder head cover on 4.0L
engines. It is connected to rear of cover on 2.5L
engines.
Fig. 3 Evaporative System Monitor Schematic—Typical
1 – DUTY CYCLE PURGE SOLENOID (DCPS) DRIVER
2 – POWERTRAIN CONTROL MODULE (PCM)
3 – 3-PORT SOLENOID DRIVER
4 – REMOTE FILTER
5 – COMBINED CANISTER VENT VALVE & LEAK DETECTION
PUMP
6 – CANISTER
7 – TANK ROLLOVER VALVE & VAPOR FLOW CONTROL
ORIFICE
8 – INTAKE MANIFOLD
9 – THROTTLE BODY
10 – DCPS
11 – SWITCH SIGNAL INPUT TO THE PCM
12 – ENGINE VACUUM LINE
XJ
EMISSION CONTROL SYSTEMS
25 - 25
DESCRIPTION AND OPERATION (Continued)