Jeep Wrangler TJ. Manual — part 608
INSTALLATION
(1) Install purge solenoid and rubber support to its
mounting bracket.
(2) Connect vacuum harness and wiring connector.
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.
CAUTION: Remove the fuel tank filler tube cap to
relieve
fuel
tank
pressure.
The
cap
must
be
removed prior to disconnecting any fuel system
component or before draining the fuel tank.
ORVR
DESCRIPTION
The ORVR (On-Board Refueling Vapor Recovery)
system consists of a unique fuel tank, flow manage-
ment valve (5) (Fig. 9) , fluid control valve, one-way
check valve and EVAP (vapor) canister (1) (Fig. 9).
A vapor line (4) and vent line (9) (Fig. 10) are also
used to connect the fuel tank into the ORVR system.
Fig. 8 EVAP/PURGE SOLENOID
1 - EVAP SYSTEM TEST PORT
2 - EVAP/PURGE SOLENOID
3 - FRONT OF BRAKE MASTER CYLINDER
4 - SOLENOID MOUNTING BRACKET
Fig. 9 ORVR VAPOR LINE
1 - EVAP CANISTER
2 - NVLD FILTER
3 - NVLD PUMP
4 - VAPOR LINES
5 - FLOW VALVE
6 - TOP OF FUEL TANK)
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EVAPORATIVE EMISSIONS
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EVAP/PURGE SOLENOID (Continued)
OPERATION
The ORVR (On-Board Refueling Vapor Recovery)
system is used to remove excess fuel tank vapors.
This is done while the vehicle is being refueled.
Fuel flowing into the fuel filler tube (approx. 1”
I.D.) creates an aspiration effect drawing air into the
fuel fill tube. During refueling, the fuel tank is
vented to the EVAP canister to capture escaping
vapors. With air flowing into the filler tube, there are
no fuel vapors escaping to the atmosphere. Once the
refueling vapors are captured by the EVAP canister,
the vehicle’s computer controlled purge system draws
vapor out of the canister for the engine to burn. The
vapor flow is metered by the purge solenoid so that
there is no, or minimal impact on driveability or
tailpipe emissions.
As fuel starts to flow through the fuel fill tube, it
opens the normally closed check valve and enters the
fuel tank. Vapor or air is expelled from the tank
through the control valve and on to the vapor canis-
ter. Vapor is absorbed in the EVAP canister until
vapor flow in the lines stops. This stoppage occurs
following fuel shut-off, or by having the fuel level in
the tank rise high enough to close the control valve.
This control valve contains a float that rises to seal
the large diameter vent path to the EVAP canister.
At this point in the refueling process, fuel tank pres-
sure increases, the check valve closes (preventing liq-
uid fuel from spiting back at the operator), and fuel
then rises up the fuel filler tube to shut off the dis-
pensing nozzle.
Fig. 10 TOP OF FUEL TANK
1 - FUEL PUMP MODULE LOCKRING
7 - SKID PLATE
2 - FUEL SUPPLY LINE
8 - FUEL FILL FITTING
3 - ELECTRICAL CONNECTOR
9 - FUEL VENT FITTING
4 - VAPOR LINE
5 - FUEL TANK MOUNTING STRAPS (2)
6 - FUEL PUMP MODULE ASSEMBLY
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EVAPORATIVE EMISSIONS
25 - 15
ORVR (Continued)
NATURAL VACUUM LEAK
DETECTION ASSEMBLY
DESCRIPTION
The Natural Vacuum Leak Detection (NVLD)
pump (3) (Fig. 11) is located behind the right-rear
wheel and system.
OPERATION
The Natural Vacuum Leak Detection (NVLD) sys-
tem is the next generation evaporative leak detection
system that will first be used on vehicles equipped
with the Next Generation Controller (NGC). This
new system replaces the leak detection pump as the
method of evaporative system leak detection. This is
to detect a leak equivalent to a 0.020
9 (0.5 mm) hole.
This system has the capability to detect holes of this
size very dependably.
The basic leak detection theory employed with
NVLD is the
9Gas Law9. This is to say that the pres-
sure in a sealed vessel will change if the temperature
of the gas in the vessel changes. The vessel will only
see this effect if it is indeed sealed. Even small leaks
will allow the pressure in the vessel to come to equi-
librium with the ambient pressure. In addition to the
detection of very small leaks, this system has the
capability of detecting medium as well as large evap-
orative system leaks.
A vent valve seals the canister vent during engine
off conditions. If the vapor system has a leak of less
than the failure threshold, the evaporative system
will be pulled into a vacuum, either due to the cool
down from operating temperature or diurnal ambient
temperature cycling. The diurnal effect is considered
one of the primary contributors to the leak determi-
nation by this diagnostic. When the vacuum in the
system exceeds about 1
9 H2O (0.25 KPA), a vacuum
switch closes. The switch closure sends a signal to
the NGC. The NGC, via appropriate logic strategies,
utilizes the switch signal, or lack thereof, to make a
determination of whether a leak is present.
The NVLD device is designed with a normally open
vacuum switch, a normally closed solenoid, and a
seal, which is actuated by both the solenoid and a
diaphragm. The NVLD is located on the atmospheric
vent side of the canister. The NVLD assembly may
be mounted on top of the canister outlet, or in-line
between the canister and atmospheric vent filter. The
normally open vacuum switch will close with about 1
9
H2O (0.25 KPA) vacuum in the evaporative system.
The diaphragm actuates the switch. This is above the
opening point of the fuel inlet check valve in the fill
tube so cap off leaks can be detected. Submerged fill
systems must have recirculation lines that do not
have the in-line normally closed check valve that pro-
tects the system from failed nozzle liquid ingestion,
in order to detect cap off conditions.
The normally closed valve in the NVLD is intended
to maintain the seal on the evaporative system dur-
ing the engine off condition. If vacuum in the evapo-
rative system exceeds 3
9 to 69 H2O (0.75 to 1.5 KPA),
the valve will be pulled off the seat, opening the seal.
This will protect the system from excessive vacuum
as well as allowing sufficient purge flow in the event
that the solenoid was to become inoperative.
The solenoid actuates the valve to unseal the can-
ister vent while the engine is running. It also will be
used to close the vent during the medium and large
leak tests and during the purge flow check. This sole-
noid requires an initial 1.5 amps of current to pull
the valve open, but after 100 mili-seconds, will be
duty cycled down to an average of about 150 mA for
the remainder of the drive cycle.
Another feature in the device is a diaphragm that
will open the seal in the NVLD with pressure in the
evaporative system. The device will
9blow off9 at
about 0.5
9 H2O (0.12 KPA) pressure to permit the
venting of vapors during refueling. An added benefit
to this is that it will also allow the tank to
9breathe9
during increasing temperatures, thus limiting the
pressure in the tank to this low level. This is benefi-
cial because the induced vacuum during a subse-
Fig. 11 ORVR VAPOR LINE
1 - EVAP CANISTER
2 - NVLD FILTER
3 - NVLD PUMP
4 - VAPOR LINES
5 - FLOW VALVE
6 - TOP OF FUEL TANK)
25 - 16
EVAPORATIVE EMISSIONS
TJ
quent declining temperature will achieve the switch
closed (pass threshold) sooner than if the tank had to
decay from a built up pressure.
The device itself has 3 wires: Switch sense, sole-
noid driver and ground. It also includes a resistor to
protect the switch from a short to battery or a short
to ground. The NGC utilizes a high-side driver to
energize and duty-cycle the solenoid.
REMOVAL
The Natural Vacuum Leak Detection (NVLD)
pump (3) (Fig. 12) and EVAP canister (1) are
attached to a common support bracket. This support
assembly is located to the rear of the right / rear tire
under the plastic wheelhouse liner. The NVLD pump
filter is also located near the EVAP canister. The
pump and filter are replaced (serviced) as one unit.
(1) Remove right/rear tire/wheel.
(2) Remove wheelhouse liner at right/rear wheel.
(3) Remove vertical support bracket (2) (Fig. 13) to
gain access to ORVR vapor lines.
(4) A vapor line (4) (Fig. 14) connects the fuel tank
to the EVAP canister and NVLD pump. This connec-
tion is made near the right/rear corner of the fuel
tank. Carefully disconnect this line. Be very careful
not to bend or kink the vapor lines. If lines leak, a
Diagnostic Trouble Code (DTC) will be set.
Fig. 12 ORVR VAPOR LINE
1 - EVAP CANISTER
2 - NVLD FILTER
3 - NVLD PUMP
4 - VAPOR LINES
5 - FLOW VALVE
6 - TOP OF FUEL TANK)
Fig. 13 EVAP CANISTER / LDP LOCATION
1 - RIGHT / REAR FENDER (WHEELHOUSE)
2 - VERTICAL SUPPORT BRACKET
3 - EVAP CANISTER
Fig. 14 ORVR VAPOR LINE
1 - EVAP CANISTER
2 - NVLD FILTER
3 - NVLD PUMP
4 - VAPOR LINES
5 - FLOW VALVE
6 - TOP OF FUEL TANK)
TJ
EVAPORATIVE EMISSIONS
25 - 17
NATURAL VACUUM LEAK DETECTION ASSEMBLY (Continued)
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