3000GT Convertible AWD V6-2972cc 3.0L DOHC Turbo (1995)
Fuel Filler Cap: Description and Operation
Fuel Filler Cap Operation
PURPOSE/OPERATION
The fuel filler cap prevents the escape of fuel vapors into the atmosphere (unless the pressure in the tank exceeds safe level, and prevents the
collapse of the fuel tank under negative pressure (vacuum). The pressure-vacuum filler cap is designed to hold a slight pressure on the fuel in the
tank, which occurs from normal heat expansion. Slightly higher pressures decrease the rate of evaporation, reducing evaporative emissions. If the
pressure within the tank exceeds a specified value, the pressure relief valve opens to relieve excess pressure. (This would occur if the pressure
relief check valve within the fuel vapor line became plugged. When vacuum in the tank exceeds specifications, the vacuum relief portion of the
filler cap allows air to enter the tank.
