Chrysler 2004 Concorde Service Manual page 1626

25 - 14 EVAPORATIVE EMISSIONS
NATURAL VAC LEAK DETECTION ASSY (Continued)
Fig. 4 LOCKING TAB
Fig. 5 ASSEMBLY REMOVED
INSTALLATION
(1) Install O-ring to EVAP canister (Fig. 6).
(2) Install NVLD assembly (Fig. 4) and twist the
assembly clockwise to lock assembly in the EVAP
canister (Fig. 5).
(3) Connect the hoses to the NVLD assembly.
(4) Connect the electrical connector to the NVLD
assembly.
(5) Install fuel tank, refer to the Fuel Delivery sec-
tion for Fuel Tank Installation.
(6) Connect the negative battery cable.
Fig. 6 O-RING
ORVR
DESCRIPTION
Onboard Refueling Vapor Recovery (ORVR) System
Schematic and components (Fig. 7).
OPERATION
The emission control principle used in the ORVR
system is that the fuel flowing into the filler tube
(approx. 1" I.D.) creates an aspiration effect which
draws air into the fill tube. During refueling, the fuel
tank is vented to the vapor canister to capture escap-
ing 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 canister, the
vehicle's computer controlled purge system draws
vapor out of the canister for the engine to burn. The
vapors 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 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 to the vapor canister. Vapor is
absorbed in the canister until vapor flow in the lines
stops, either following shut-off or by having the fuel
level in the tank rise high enough to close the control
valve. The control valve contains a float that rises to
seal the large diameter vent path to the canister. At
this point in the fueling of the vehicle, the tank pres-
sure increase, the check valve closes (preventing tank
fuel from spiting back at the operator), and fuel then
rises up the filler tube to shut-off the dispensing noz-
zle.
LH