ENGINE - 2AZ-FXE ENGINE
02HEG33Y
THS
ECU
To Intake Manifold
Purge VSV
(Open)
Canister Filter
Fresh Air Line
Purge Line
Fuel Tank
Pressure Sensor
Fuel Outlet
Valve (Close)
Fuel Vapor-containment
Valve (Close)
Canister
EG-63
2) Purge Flow Control
a. General
When the engine has satisfied predetermined conditions (closed loop, engine coolant temp. above
70
C [162
F], etc), stored fuel vapor is purged in the canister whenever the purge VSV is opened
by the THS ECU. The THS ECU will change the duty ratio cycle of the purge VSV, thus controlling
purge flow volume. Purge flow volume is determined by intake manifold pressure and the duty ratio
cycle of the purge VSV. Atmospheric pressure is allowed into the canister to ensure that purge flow
is constantly maintained whenever purge vacuum is applied to the canister.
Due to the adoption of a fuel vapor-containment system, purge flow performs two types of
operations, depending on the internal pressure of the fuel tank.
b. Fuel Tank Internal Pressure is Near Atmospheric Pressure
If the internal pressure in the fuel tank is near the atmospheric pressure, the THS ECU will not open
the fuel vapor-containment valve even if the purge VSV is open. At this time, the fuel vapor that is
absorbed in the canister is drawn inside the engine and burned.