sion of fuel tank vapors into the atmosphere. When
fuel evaporates in the fuel tank, the vapors pass
through vent hoses or tubes to a charcoal filled evap-
orative canister. The canister temporarily holds the
vapors. The Powertrain Control Module (PCM) allows
intake manifold vacuum to draw vapors into the com-
bustion chambers during certain operating condi-
tions.

All engines use a duty-cycle purge system. The

PCM controls vapor flow by operating the duty-cycle

EVAP purge solenoid. Refer to Duty-Cycle EVAP
Canister Purge Solenoid.

An ORVR system is used. This system is part of

the EVAP Control System. Refer to On-Board Refuel-
ing Vapor Recovery (ORVR) for information.

When equipped with certain emissions packages, a

Leak Detection Pump (LDP) will be used as part of
the evaporative system for OBD II requirements.
Also refer to Leak Detection Pump.

NOTE: The evaporative system uses specially man-
ufactured lines/hoses. If replacement becomes nec-
essary, only use fuel resistant hose.

25 - 10

EVAPORATIVE EMISSIONS

SPECIFICATIONS

TORQUE - EMISSIONS

DESCRIPTION

N-m

Ft. Lbs.

In. Lbs.

EVAP Canister Mounting

Nuts

Leak Detection Pump

Filter Mounting Bolt

LDP Pump Mounting Bolts

EVAP Canister/LDP

Mounting Bracket-to-Body

Nuts

250

EVAP Canister/LDP

Mounting Bracket-to-Body

Bolts

212

CCV SYSTEM

DESCRIPTION - CCV SYSTEM

The 4.0L 6-cylinder engine is equipped with a

Closed Crankcase Ventilation (CCV) system and a
fixed orifice valve (Fig. 1). The 2.4L 4-cylinder uses a
PCV valve. Refer to PCV Valve for 2.4L information.

OPERATION - CCV SYSTEM

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 the top of the cylinder
head (valve) cover. The vacuum fitting contains a
fixed orifice of a calibrated size. It meters the
amount of crankcase vapors drawn out of the engine.

When the engine is operating, fresh air enters the

engine and mixes with crankcase vapors. Manifold
vacuum draws the vapor/air mixture through the
fixed orifice and into the intake manifold. The vapors
are then consumed during combustion.

DIAGNOSIS AND TESTING - CCV SYSTEM

TESTING/CLEANING

The Crankcase Ventilation (CCV) system performs

the same function as a conventional PCV system, but
does not use a vacuum controlled valve. A vacuum
fitting containing a fixed orifice of a calibrated size is
used. It meters the amount of crankcase vapors
drawn out of the engine.

(1) Check each CCV system tube (line) for leaks,

cracks, kinks or bends. Replace as necessary

(2) Disconnect each CCV tube.
(3) Remove fixed orifice fitting from valve cover.
(4) Blow compressed air through each tube, and

the fixed orifice fitting. Check for blockage or restric-
tions. If cleaning is necessary, spray a soapy-type all-
purpose cleaner into each component and blow out.
After restriction is cleared, rinse out component with
clear water. Blow water from component and install
to vehicle. To prevent damage to plastic compo-
nents, never spray carburetor-type cleaner into

Fig. 1 CRANKCASE VENTILATION (CCV) FITTING -

4.0L

1 - AIR CLEANER ASSEMBLY
2 - AIR INTAKE TUBE
3 - FIXED ORIFICE FITTING
4 - VACUUM LINE
5 - AIR INLET FITTING

EVAPORATIVE EMISSIONS

25 - 11

EVAPORATIVE EMISSIONS (Continued)

any of the plastic tubes or the fixed orifice fit-
ting. Never attempt to clean the fixed orifice
fitting with a metal object as calibration could
be affected. If fixed fitting cannot be cleared,
replace it.

PCV VALVE

DESCRIPTION

2.4L

The 2.4L 4-cylinder engine is equipped with a

closed crankcase ventilation system and a Positive
Crankcase Ventilation (PCV) valve.

This system consists of:
• a PCV valve attached to the left/front side of the

valve cover (Fig. 2). It is secured with 1 bolt. An
o-ring is used to seal valve to valve cover (Fig. 3).
Another type of threaded PCV valve may be used
(Fig. 4).

• the air cleaner housing

• tubes and hoses to connect the system compo-

nents.

OPERATION

2.4L

The PCV system operates by engine intake mani-

fold vacuum. Filtered air is routed into the crankcase
through the air cleaner hose and crankcase breath-
er(s) (if used). The metered air, along with crankcase

vapors, are drawn through the PCV valve and into a
passage in the intake manifold. The PCV system
manages crankcase pressure and meters blow-by
gases to the intake system, reducing engine sludge
formation.

The PCV valve contains a spring loaded plunger.

This plunger meters the amount of crankcase vapors

Fig. 2 PCV VALVE LOCATION - 2.4L

1 - PCV VALVE
2 - HOSE
3 - MOUNTING BOLT
4 - VALVE COVER (LEFT SIDE)

Fig. 3 PCV VALVE AND O-RING - 2.4L

1 - PCV VALVE
2 - O-RING
3 - MOUNTING BOLT

Fig. 4 PCV VALVE - 2.4L - THREADED

1 - PCV VALVE (THREADED)
2 - VALVE COVER (LEFT SIDE)

25 - 12

EVAPORATIVE EMISSIONS

CCV SYSTEM (Continued)

routed into the combustion chamber based on intake
manifold vacuum.

TYPICAL PCV valves are shown in (Fig. 5), (Fig.

6) and (Fig. 7).

When the engine is not operating, or during an

engine pop-back, the spring forces the plunger back
against the seat (Fig. 5). This will prevent vapors
from flowing through the valve.

During periods of high manifold vacuum, such as

idle or cruising speeds, vacuum is sufficient to com-
pletely compress spring. It will then pull the plunger
to the top of the valve (Fig. 6). In this position there
is minimal vapor flow through the valve.

During periods of moderate manifold vacuum, the

plunger is only pulled part way back from inlet. This
results in maximum vapor flow through the valve
(Fig. 7).

REMOVAL

2.4L

The PCV valve is attached to the left/front side of

the valve cover (Fig. 2). It is secured with 1 bolt. An

o-ring is used to seal valve to valve cover (Fig. 3).
Another type of threaded PCV valve may be used
(Fig. 4).

(1) Remove hose from valve. Check condition of

hose.

(2) Bolted PCV Valve:

(a) Remove 1 bolt.
(b) Remove PCV valve from valve cover.
(c) Check condition of valve o-ring.

(3) Threaded PCV Valve:

(a) Unscrew valve from valve cover.

EVAP/PURGE SOLENOID

DESCRIPTION

The duty cycle EVAP canister purge solenoid (DCP)

regulates the rate of vapor flow from the EVAP can-
ister to the intake manifold. The Powertrain Control
Module (PCM) operates the solenoid.

OPERATION

During the cold start warm-up period and the hot

start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged. The
PCM de-energizes the solenoid during open loop oper-
ation.

The engine enters closed loop operation after it

reaches a specified temperature and the time delay
ends. During closed loop operation, the PCM cycles
(energizes and de-energizes) the solenoid 5 or 10
times per second, depending upon operating condi-
tions. The PCM varies the vapor flow rate by chang-
ing solenoid pulse width. Pulse width is the amount
of time that the solenoid is energized. The PCM
adjusts solenoid pulse width based on engine operat-
ing condition.

REMOVAL

The duty cycle EVAP canister purge solenoid is

located in the engine compartment near the front of
the brake master cylinder (Fig. 8). It is attached to a
slip-on type bracket.

The EVAP System Test Port is located near the

EVAP/Purge Solenoid (Fig. 8).

(1) Disconnect electrical wiring connector at sole-

noid.

(2) Disconnect vacuum lines/hoses at solenoid.
(3) Lift solenoid and rubber solenoid support from

mounting bracket.

Fig. 5 ENGINE OFF OR ENGINE BACKFIRE - NO

VAPOR FLOW

Fig. 6 HIGH INTAKE MANIFOLD VACUUM - MINIMAL

VAPOR FLOW

Fig. 7 MODERATE INTAKE MANIFOLD VACUUM -

MAXIMUM VAPOR FLOW

EVAPORATIVE EMISSIONS

25 - 13

PCV VALVE (Continued)

Content .. 605 606 607 608 ..