B3000 2WD V6-3.0L OHV (1994)
Fuel Filler Cap: Description and Operation
PURPOSE
The pressure-vacuum filler cap is designed to hold a slight pressure on the fuel. Since the evaporation rate decreases under slightly higher
pressures, the cap helps to reduce evaporative emissions.
Fuel Tank Pressure/Vacuum Filler Cap
OPERATION
A rubber seal around the inside lip of the cap prevents fuel vapor from escaping to the atmosphere, as well as prevent fuel from spilling in the
event of vehicle roll-over.
When vacuum in the tank exceeds a pressure differential to atmospheric pressure, the vacuum relief valve will allow atmospheric pressure to enter
the tank.
If fuel tank pressure becomes 0.14 kP cm sq (1.8 psi) above atmospheric pressure, the pressure relief portion of the cap will open to the
atmosphere.
