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 canister. 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 pressure
increases, the check valve closes (preventing liquid fuel from spiting back at the operator), and fuel then rises up
the fuel filler tube to shut off the dispensing nozzle.
VALVE - PCV
DESCRIPTION
3.7L V-6 / 4.7L V-8
The 3.7L V-6 and 4.7L V-8 engines are equipped with a closed crankcase ventilation system and a Positive Crank-
case Ventilation (PCV) valve.
This system consists of a PCV valve (6) sealed to the
oil filler housing with an o-ring (1), the air cleaner
housing, and tubes and hoses to connect the system
components.
25 - 14
EVAPORATIVE EMISSIONS
ND