Subaru 2002 Impreza Service Manual page 120

EVAPORATIVE EMISSION CONTROL SYSTEM
Emission Control
(Aux.
Emission Control Devices)
C: FUEL TANK CAP
The fuel tank cap has a relief valve which prevents development of vacuum in the fuel tank in the
event of a problem with the fuel vapor line.
When there is no problem with the fuel vapor line, the filler pipe is sealed at the portion (A) and
by the seal pressed against the filler pipe end. If vacuum develops in the fuel tank, the atmospheric
pressure forces the spring down to open the valve; consequently outside air flows into the fuel tank,
thus controlling the inside pressure.
NF0470
(1)
Seal
(2) Spring
(3) Valve
(4) Filter
EC-12