sion of fuel tank vapors into the atmosphere. When
fuel evaporates in the fuel tank, the vapors pass
through vent hoses or tubes to an activated carbon
filled evaporative canister. The canister temporarily
holds the vapors. The Powertrain Control Module
(PCM) allows intake manifold vacuum to draw
vapors into the combustion chambers during certain
operating conditions (Fig. 1).

All engines use a proportional purge solenoid sys-

tem. The PCM controls vapor flow by operating the
purge solenoid. Refer to Proportional Purge Solenoid
in this section.

NOTE: The evaporative system uses specially man-
ufactured hoses. If they need replacement, only use
fuel resistant hose. Also the hoses must be able to
pass an Ozone compliance test.

NOTE: For more information on Onboard Refueling
Vapor Recovery (ORVR), refer to the Fuel Delivery
section.

25 - 10

EVAPORATIVE EMISSIONS

SPECIFICATIONS

TORQUE

DESCRIPTION

N·m

Ft. Lbs.

In. Lbs.

PCV VAlve 3.3/3.8L

6.3

Fig. 1 ORVR System Schematic

1 - FUEL TANK (PLASTIC)
2 - FUEL FILLER TUBE
3 - FUEL CAP (PRESSURE/RELIEF)
4 - FILL TUBE TO FUEL TANK CONNECTOR (ELASTOMERIC)
5 - TANK VENT/ROLLOVER VALVE(S)
6 - VAPOR RECIRCULATION LINE
7 - TANK VAPOR LINE
8 - VAPOR LINE TO CANISTER
9 - CHECK VALVE (N/C)
10 - CONTROL VALVE
11 - NATURAL VACUUM LEAD DETECTION (NVLD)

12 - LIQUID SEPARATOR (IF EQUIPPED)
13 - ENGINE WIRING HARNESS TO NVLD
14 - VAPOR CANISTER
15 - PURGE LINE
16 - PURGE DEVICE
17 - WITHOUT NVLD
18 - BREATHER ELEMENT
19 - FLOW CONTROL ORIFICE
20 - SERVICE PORT
21 - WITH NVLD

EVAPORATIVE EMISSIONS

25 - 11

EVAPORATIVE EMISSIONS (Continued)

EVAP/PURGE SOLENOID

DESCRIPTION

All vehicles use a proportional purge solenoid (Fig.

2). The solenoid regulates the rate of vapor flow from
the EVAP canister to the throttle body. The 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 proportional purge solenoid operates at a fre-

quency of 200 hz and is controlled by an engine con-
troller circuit that senses the current being applied
to the proportional purge solenoid and then adjusts
that current to achieve the desired purge flow. The
proportional purge solenoid controls the purge rate of
fuel vapors from the vapor canister and fuel tank to
the engine intake manifold.

REMOVAL

The solenoid attaches to a bracket near the radia-

tor on the passenger side of vehicle (Fig. 3). The sole-
noid will not operate unless it is installed correctly.

(1) Disconnect electrical connector from solenoid.
(2) Disconnect vacuum tubes from solenoid.
(3) Remove solenoid from bracket.

INSTALLATION

The solenoid attaches to a bracket near the radia-

tor on the passenger side of vehicle. The solenoid will
not operate unless it is installed correctly.

The top of the solenoid has TOP printed on it. The

solenoid will not operate unless it is installed cor-
rectly.

(1) Install solenoid on bracket.
(2) Connect vacuum tube to solenoid.
(3) Connect electrical connector to solenoid.

FUEL FILLER CAP

DESCRIPTION

The plastic fuel fill cap is threaded/quarter turn

onto the end of the fuel filler tube. It’s purpose is to
retain vapors and fuel in the fuel tank.

OPERATION

The fuel filler cap incorporates a two-way relief

valve that is closed to atmosphere during normal
operating conditions. The relief valve is calibrated to
open when a pressure of 17 kPa (2.5 psi) or vacuum
of 2 kPa (0.6 in. Hg) occurs in the fuel tank. When
the pressure or vacuum is relieved, the valve returns
to the normally closed position.

CAUTION: Remove the fuel filler cap to release fuel
tank pressure before disconnecting any fuel system
component.

Fig. 2 Proportional Purge Solenoid

Fig. 3 EVAP PURGE SOLENOID

1 - EVAP Purge Solenoid
2 - EGR VAlve
3 - Generator

25 - 12

EVAPORATIVE EMISSIONS

NATURAL VAC LEAK
DETECTION ASSY

REMOVAL

(1) Disconnect thew negative battery cable.
(2) Raise vehicle and support (Fig. 4).

(3) Unlock and disconnect the electrical connector.
(4) Remove the hoses from the NVLD valve.
(5) Remove the 2 fasteners.
(6) Remove the valve and bracket from vehicle

(Fig. 5).

(7) Remove valve from bracket (Fig. 6).

INSTALLATION

(1) Install NVLD valve to the bracket (Fig. 6).
(2) Install valve and bracket to the vehicle (Fig. 5).
(3) Install the 2 mounting bolts and tighten.
(4) Install the electrical connector and lock.
(5) Install the 2 hoses and lock the clamps.
(6) Lower vehicle.

LEAK DETECTION PUMP

REMOVAL

(1) Disconnect the negative battery cable.
(2) Raise and support the vehicle.
(3) Remove 3 hoses (Fig. 7).
(4) Remove the electrical connector (Fig. 8).
(5) Remove the 3 screws and remove LDP pump.

INSTALLATION

(1) Install LDP.
(2) Install the 3 screws and tighten (Fig. 8).
(3) Install the electrical connector.
(4) Install the 3 hoses (Fig. 7).
(5) Lower vehicle.
(6) Connect the negative battery cable.

Fig. 4 NVLD LOCATION

Fig. 5 NVLD REMOVAL/INSTALLATION

Fig. 6 NVLD VALVE AND BRACKET

EVAPORATIVE EMISSIONS

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