2002 JEEP GRAND CHEROKEE Engine

NOTE: The evaporative system uses specially man-
ufactured lines/hoses. If replacement becomes nec-
essary, only use fuel resistant, low permeation
hose.
Certain components can be found in (Fig. 1).
DESCRIPTION - CCV SYSTEM
The 4.0L 6±cylinder engine is equipped with a
Crankcase Ventilation (CCV) system. The system
consists of:
²A fixed orifice fitting of a calibrated size. This
fitting is pressed into a rubber grommet located on
the top/rear of cylinder head (valve) cover (Fig. 2).
²a pair of breather tubes (lines) to connect the
system components.
²the air cleaner housing.
²an air inlet fitting (Fig. 2).
DESCRIPTION - PCV SYSTEM
The 4.7L V-8 engine is equipped with a closed
crankcase ventilation system and a Positive Crank-
case Ventilation (PCV) valve.
This system consists of:
Fig. 1 ORVR / LDP COMPONENTS
1 - FUEL TANK (LEFT SIDE) 6 - EVAP CANISTER
2 - FRAME RAIL (LEFT-REAR OUTSIDE) 7 - LDP FILTER
3 - FUEL VENT TUBE 8 - TWO-PIECE SUPPORT BRACKET
4 - FUEL FILL TUBE 9 - LEAK DETECTION PUMP (LDP)
5 - CONTROL VALVE
Fig. 2 CCV SystemÐ4.0L Engine
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
WJEVAPORATIVE EMISSIONS 25 - 25
EVAPORATIVE EMISSIONS (Continued)

²a PCV valve mounted to the oil filler housing
(Fig. 3). The PCV valve is sealed to the oil filler
housing with an o-ring.
²the air cleaner housing
²two interconnected breathers threaded into the
rear of each cylinder head (Fig. 4).
²tubes and hose to connect the system compo-
nents.
OPERATION
OPERATION - 4.0L CCV SYSTEM
The CCV system performs the same function as a
conventional PCV system, but does not use a vacuum
controlled PCV valve.
The fixed orifice fitting 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. Engine vac-uum draws the vapor/air mixture through the fixed
orifice and into the intake manifold. The vapors are
then consumed during engine combustion.
OPERATION - 4.7L PCV SYSTEM
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-
ers. 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
routed into the combustion chamber based on intake
manifold vacuum.
TYPICALPCV 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.
Fig. 3 PCV Valve/Oil Filler Tube (Housing)Ð4.7L
Engine
1 - O-RING
2 - LOCATING TABS
3 - CAM LOCK
4 - OIL FILLER TUBE
5 - PCV LINE/HOSE
6 - P C V VA LV E
Fig. 4 PCV System Hoses/TubesÐ4.7L Engine
1 - FRESH AIR FITTING
2 - CONNECTING TUBES/HOSES
3 - CRANKCASE BREATHERS (2)
4 - RUBBER HOSE
5 - AIR CLEANER RESONATOR
25 - 26 EVAPORATIVE EMISSIONSWJ
EVAPORATIVE EMISSIONS (Continued)

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).
SPECIFICATIONS
TORQUE - EVAPORATION SYSTEM
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Crankcase Breathers - 3.7L /
4.7L12 - 106
EVAP Canister Mounting 11 - 100
EVAP Canister Purge
Solenoid Mounting Nuts9- 80
LDP Pump-to-Support Bracket 2 - 20
LDP Pump Support
Bracket-to-Frame28 - 250
Fig. 5 Engine Off or Engine Pop-BackÐNo Vapor
FlowFig. 6 High Intake Manifold VacuumÐMinimal Vapor
Flow
Fig. 7 Moderate Intake Manifold VacuumÐMaximum
Vapor Flow
WJEVAPORATIVE EMISSIONS 25 - 27
EVAPORATIVE EMISSIONS (Continued)

CCV HOSE
DIAGNOSIS AND TESTING - CCV SYSTEM -
4.0L
Before attempting diagnosis, be sure locations of
fixed orifice fitting and air inlet fitting (Fig. 8) have
not been inadvertently exchanged. The fixed orifice
fitting is light grey in color and is located atrearof
valve cover. The air inlet fitting is black in color and
is located atfrontof valve cover.
(1) Pull fixed orifice fitting (Fig. 8) from valve
cover and leave tube attached.
(2) Start engine and bring to idle speed.
(3) If fitting is not plugged, a hissing noise will be
heard as air passes through fitting orifice. Also, a
strong vacuum should be felt with a finger placed at
fitting inlet.
(4) If vacuum is not present, remove fitting orifice
fitting from tube. Start engine. If vacuum can now be
felt, replace fixed orifice fitting. Do not attempt to
clean plastic fitting.
(5) If vacuum is still not felt at hose, check line/
hose for kinks or for obstruction. If necessary, clean
out intake manifold fitting at intake manifold. Do
this by turning a 1/4 inch drill (by hand) through the
fitting to dislodge any solid particles. Blow out thefitting with shop air. If necessary, use a smaller drill
to avoid removing any metal from the fitting.
(6) Return fixed orifice fitting to valve cover and
leave tube attached.
(7) Disconnect air inlet fitting and its attached
hose at front of valve cover (Fig. 8). Start engine and
bring to idle speed. Hold a piece of stiff paper (such
as a parts tag) loosely over the rubber grommet
(opening) of the disconnected air inlet fitting.
(8) The paper should be drawn against the rubber
grommet with noticeable force. This will be after
allowing approximately one minute for crankcase
pressure to reduce.
(9) If vacuum is not present, check breather hoses/
tubes/lines for obstructions or restrictions.
(10) After testing, reconnect all system hoses/
tubes/lines.
REMOVAL - FIXED ORIFICE FITTING
When installing fixed orifice fitting, be sure loca-
tions of fixed orifice fitting and air inlet fitting (Fig.
9) have not been inadvertently exchanged. The fixed
orifice fitting is light grey in color and is located at
rearof valve cover. The air inlet fitting is black in
color and is located atfrontof valve cover.
(1) Pull fixed orifice fitting (Fig. 9) from valve
cover grommet.
(2) Separate fitting from CCV breather tube.
Fig. 8 Fixed Orifice Fitting and CCV SystemÐ4.0L
Engine
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
Fig. 9 FIXED ORIFICE FITTING - 4.0L
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
25 - 28 EVAPORATIVE EMISSIONSWJ

INSTALLATION - FIXED ORIFICE FITTING
When installing fixed orifice fitting, be sure loca-
tions of fixed orifice fitting and air inlet fitting (Fig.
9) have not been inadvertently exchanged. The fixed
orifice fitting is light grey in color and is located at
rearof valve cover. The air inlet fitting is black in
color and is located atfrontof valve cover.
(1) Connect fitting to CCV breather tube.
(2) Return fixed orifice fitting to valve cover grom-
met.
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 evaporative (EVAP) canister purge
solenoid is located in the engine compartment near
the brake master cylinder (Fig. 10).
(1) Disconnect electrical connector at solenoid.
(2) Disconnect vacuum lines at solenoid.
(3) Lift solenoid slot (Fig. 10) from mounting
bracket for removal.
INSTALLATION
(1) Position solenoid slot to mounting bracket.
(2) Connect vacuum lines to solenoid. Be sure vac-
uum lines are firmly connected and not leaking or
damaged. If leaking, a Diagnostic Trouble Code
(DTC) may be set with certain emission packages.
(3) Connect electrical connector to solenoid.
FUEL FILLER CAP
DESCRIPTION
The plastic fuel tank filler tube cap is threaded
onto the end of the fuel fill tube. Certain models are
equipped with a 1/4 turn cap.
OPERATION
The loss of any fuel or vapor out of fuel filler tube
is prevented by the use of a pressure-vacuum fuel fill
cap. Relief valves inside the cap will release fuel tank
pressure at predetermined pressures. Fuel tank vac-
uum will also be released at predetermined values.
This cap must be replaced by a similar unit if
replacement is necessary. This is in order for the sys-
tem to remain effective.
CAUTION: Remove fill cap before servicing any fuel
system component to relieve tank pressure. If
equipped with a California emissions package and a
Leak Detection Pump (LDP), the cap must be tight-
ened securely. If cap is left loose, a Diagnostic
Trouble Code (DTC) may be set.
REMOVAL
If replacement of the 1/4 turn fuel tank filler tube
cap is necessary, it must be replaced with an identi-
cal cap to be sure of correct system operation.
Fig. 10 EVAP/PURGE SOLENOID LOCATION
1 - BRAKE MASTER CYLINDER
2 - EVAP SOLENOID
3 - SLOT
4 - ELEC. CONNEC.
5 - VACUUM LINE CONNEC.
6 - TEST PORT
WJEVAPORATIVE EMISSIONS 25 - 29
CCV HOSE (Continued)

OPERATION
The main purpose of the LDP is to pressurize the
fuel system for leak checking. It closes the EVAP sys-
tem vent to atmospheric pressure so the system can
be pressurized for leak testing. The diaphragm is
powered by engine vacuum. It pumps air into the
EVAP system to develop a pressure of about 7.59
H2O (1/4) psi. A reed switch in the LDP allows the
PCM to monitor the position of the LDP diaphragm.
The PCM uses the reed switch input to monitor how
fast the LDP is pumping air into the EVAP system.
This allows detection of leaks and blockage. The LDP
assembly consists of several parts (Fig. 12). The sole-
noid is controlled by the PCM, and it connects the
upper pump cavity to either engine vacuum or atmo-
spheric pressure. A vent valve closes the EVAP sys-
tem to atmosphere, sealing the system during leak
testing. The pump section of the LDP consists of a
diaphragm that moves up and down to bring air in
through the air filter and inlet check valve, and
pump it out through an outlet check valve into the
EVAP system. The diaphragm is pulled up by engine
vacuum, and pushed down by spring pressure, as the
LDP solenoid turns on and off. The LDP also has a
magnetic reed switch to signal diaphragm position to
the PCM. When the diaphragm is down, the switch is
closed, which sends a 12 V (system voltage) signal to
the PCM. When the diaphragm is up, the switch is
open, and there is no voltage sent to the PCM. This
allows the PCM to monitor LDP pumping action as it
turns the LDP solenoid on and off.
LDP AT REST (NOT POWERED)
When the LDP is at rest (no electrical/vacuum) the
diaphragm is allowed to drop down if the internal
(EVAP system) pressure is not greater than the
return spring. The LDP solenoid blocks the engine
vacuum port and opens the atmospheric pressure
port connected through the EVAP system air filter.
The vent valve is held open by the diaphragm. This
allows the canister to see atmospheric pressure (Fig.
13).
DIAPHRAGM UPWARD MOVEMENT
When the PCM energizes the LDP solenoid, the
solenoid blocks the atmospheric port leading through
the EVAP air filter and at the same time opens the
engine vacuum port to the pump cavity above the
diaphragm. The diaphragm moves upward when vac-
uum above the diaphragm exceeds spring force. This
upward movement closes the vent valve. It also
causes low pressure below the diaphragm, unseating
the inlet check valve and allowing air in from the
EVAP air filter. When the diaphragm completes its
upward movement, the LDP reed switch turns from
closed to open (Fig. 14).
DIAPHRAGM DOWNWARD MOVEMENT
Based on reed switch input, the PCM de-energizes
the LDP solenoid, causing it to block the vacuum
port, and open the atmospheric port. This connects
the upper pump cavity to atmosphere through the
EVAP air filter. The spring is now able to push the
diaphragm down. The downward movement of the
diaphragm closes the inlet check valve and opens the
outlet check valve pumping air into the evaporative
system. The LDP reed switch turns from open to
closed, allowing the PCM to monitor LDP pumping
(diaphragm up/down) activity (Fig. 15). During the
pumping mode, the diaphragm will not move down
far enough to open the vent valve. The pumping cycle
is repeated as the solenoid is turned on and off.
When the evaporative system begins to pressurize,
the pressure on the bottom of the diaphragm will
begin to oppose the spring pressure, slowing the
pumping action. The PCM watches the time from
when the solenoid is de-energized, until the dia-
phragm drops down far enough for the reed switch to
Fig. 12 EVAP LEAK DETECTION SYSTEM
COMPONENTS
1 - Reed Switch
2 - Solenoid
3 - Spring
4 - Pump Cavity
5 - Diaphragm
6 - Inlet Check Valve
7 - Vent Valve
8 - From Air Filter
9 - To Canister
10 - Outlet Check Valve
11 - Engine Vacuum
WJEVAPORATIVE EMISSIONS 25 - 31
LEAK DETECTION PUMP (Continued)

change from opened to closed. If the reed switch
changes too quickly, a leak may be indicated. The
longer it takes the reed switch to change state, the
tighter the evaporative system is sealed. If the sys-
tem pressurizes too quickly, a restriction somewhere
in the EVAP system may be indicated.
PUMPING ACTION
Action : During portions of this test, the PCM uses
the reed switch to monitor diaphragm movement.
The solenoid is only turned on by the PCM after the
reed switch changes from open to closed, indicating
that the diaphragm has moved down. At other times
during the test, the PCM will rapidly cycle the LDP
solenoid on and off to quickly pressurize the system.
During rapid cycling, the diaphragm will not move
enough to change the reed switch state. In the state
of rapid cycling, the PCM will use a fixed time inter-
val to cycle the solenoid. If the system does not pass
the EVAP Leak Detection Test, the following DTCs
may be set:
²P0442 - EVAP LEAK MONITOR 0.0409LEAK
DETECTED
²P0455 - EVAP LEAK MONITOR LARGE LEAK
DETECTED²P0456 - EVAP LEAK MONITOR 0.0209LEAK
DETECTED
²P1486 - EVAP LEAK MON PINCHED HOSE
FOUND
²P1494 - LEAK DETECTION PUMP SW OR
MECH FAULT
²P1495 - LEAK DETECTION PUMP SOLENOID
CIRCUIT
DIAGNOSIS AND TESTING - ENABLING
CONDITIONS TO RUN EVAP LEAK DETECTION
TEST
²Cold start: with ambient temperature (obtained
from modeling the inlet air temperature sensor on
passenger vehicles and the battery temperature sen-
sor on Jeep & Dodge Truck vehicles) between 4É C
(40É F) and 32É C (90É F) for 0.040 leak. Between 4É
C (40É F) and 29É C (85É F) for 0.020 leak.
²Engine coolant temperature within:-12É to -8É C
(10É to 18É F) of battery/ambient.
²Battery voltage between 10 and 15 volts.
²Low fuel warning light off (fuel level must be
between 15% and 85%.
²MAP sensor reading 22 in Hg or above (This is
the manifold absolute pressure, not vacuum).
Fig. 13 LDP AT REST
1 - Diaphragm
2 - Inlet Check Valve (Closed)
3 - Vent Valve (Open)
4 - From Air Filter
5 - To Canister
6 - Outlet Check Valve (Closed)
7 - Engine Vacuum (Closed)
Fig. 14 DIAPHRAGM UPWARD MOVEMENT
1 - Diaphragm
2 - Inlet Check Valve (Open)
3 - Vent Valve (Closed)
4 - From Air Filter
5 - To Canister
6 - Outlet Check Valve (Closed)
7 - Engine Vacuum (Open)
25 - 32 EVAPORATIVE EMISSIONSWJ
LEAK DETECTION PUMP (Continued)

²No engine stall during test.
NOTE: IF BATTERY VOLTAGE DROPS BELOW 10
VOLTS FOR MORE THAN 5 SECONDS DURING
ENGINE CRANKING, THE EVAP LEAK DETECTION
TEST WILL NOT RUN.
NOTE: THE FOLLOWING VALUES ARE APPROXI-
MATE AND VEHICLE SPECIFIC. USE THE VALUES
SEEN IN PRE TEST/MONITOR TEST SCREEN ON
THE DRB IIIT. SEE TSB 25-02-98 FOR MORE
DETAIL.
A DTC will not be set if a one-trip fault is set or if
the MIL is illuminated for any of the following:
²Purge Solenoid Electrical Fault
²All TPS Faults
²All Engine Controller Self Test Faults
²LDP Pressure Switch Fault
²All Cam and/or Crank Sensor Fault
²EGR Solenoid Electrical Fault
²All MAP Sensor Faults
²All Injector Faults
²Ambient/Battery Temperature Sensor Electrical
Faults²Baro Out of Range
²Vehicle Speed Faults
²All Coolant Sensor Faults
²LDP Solenoid Circuit
NOTE: IF BATTERY TEMPERATURE IS NOT WITHIN
RANGE, OR IF THE ENGINE COOLANT TEMPERA-
TURE IS NOT WITHIN A SPECIFIED RANGE OF THE
BATTERY TEMPERATURE, THE PCM WILL NOT
RUN TESTS FOR DTC P1494, P1486, P0442, P0455
AND P0441. THESE TEMPERATURE CALIBRATIONS
MAY BE DIFFERENT BETWEEN MODELS.
SECTION 1 - P1495 Leak Detection Pump
Solenoid Circuit-When the ignition key is turned
to9ON9, the LDP diaphragm should be in the down
position and the LDP reed switch should be closed. If
the EVAP system has residual pressure, the LDP dia-
phragm may be up. This could result in the LDP reed
switch being open when the key is turned to9ON9
and a P1494 fault could be set because the PCM is
expecting the reed switch to be closed.
After the key is turned9ON9, the PCM immedi-
ately tests the LDP solenoid circuit for electrical
faults. If a fault is detected, DTC P1495 will set, the
Fig. 15 DIAPHRAGM DOWNWARD MOVEMENT
1 - Diaphragm
2 - Inlet Check Valve (Closed)
3 - Vent Valve (Closed)
4 - From Air Filter
5 - To Canister
6 - Outlet Check Valve (Open)
7 - Engine Vacuum (Closed)EVAP LDP TEST SEQUENCE
1 - IGNITION SWITCH
2 - LDP DIAPHRAM
3 - LDP SWITCH
4 - LDP SOLENOID
5 - SECTION 1
6 - SECTION 2
7 - SECTION 3
8 - SECTION 4
9 - SECTION 5
10 - 3 TEST CYCLES TO TEST FOR BLOCKAGE
11- RAPID PUMP CYCLING FOR 70 CYCLES
WJEVAPORATIVE EMISSIONS 25 - 33
LEAK DETECTION PUMP (Continued)