Service Manuals, User Guides, Schematic Diagrams or docs for : . Car Manuals Subaru Impreza 2001-2002.2004-2007 Approved Subaru Impreza 2004 WRX STi 08. MECHANISM AND FUNCTION 13. EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES) 08. On-board Refueling Vapor Recovery (ORVR) System
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W1860BE.book Page 23 Tuesday, January 28, 2003 11:01 PM
ON-BOARD REFUELING VAPOR RECOVERY (ORVR) SYSTEM
EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES)
8. On-board Refueling Vapor Recovery (ORVR) System
A: GENERAL
The on-board refueling vapor recovery system allows the fuel vapors in the fuel tank to be intro-
duced directly into the canister through the vent valve when the fuel tank inside pressure increases
as a result of refueling.
The diagnosis of the system is performed by monitoring the fuel tank inside pressure data from the
fuel tank pressure sensor while forcibly closing the drain valve.
B: OPERATION
While driving
Since the back side of the diaphragm in the pressure control solenoid valve is open to the atmo-
sphere, the diaphragm is held pressed by the atmospheric pressure in the position where only the
external air is introduced into the canister. When the fuel vapor pressure acting on the other side of
the diaphragm increases and overcomes the atmospheric pressure, it pushes the diaphragm and
opens the port through which the fuel vapors make their way to the canister.
(4)
(3)
(5)
(1)
(2)
EC-00032
(1) Canister (4) Intake manifold
(2) Pressure control solenoid valve (5) Shut-off valve: open
(3) Purge control solenoid valve
EC(H4DOTC)-23
W1860BE.book Page 24 Tuesday, January 28, 2003 11:01 PM
ON-BOARD REFUELING VAPOR RECOVERY (ORVR) SYSTEM
EMISSION CONTROL (AUX. EMISSION CONTROL DEVICES)
While refueling
As the fuel enters the fuel tank, the tank inside pressure increases. When the inside pressure be-
comes higher than the atmospheric pressure, the port of the vent valve opens, allowing the fuel va-
pors to be introduced into the canister through the vent line. The fuel vapors are absorbed by
charcoal in the canister, so the air discharged from the drain valve contains no fuel. When a filler
gun is inserted, the shut-off valve closes the evaporation line.
(4)
(3)
(1)
(2)
(5)
EC-00033
(1) Canister (4) Shut-off valve: closed
(2) Pressure control solenoid valve (5) Filler gun
(3) Vent valve
EC(H4DOTC)-24
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