D50/Power Ram 50 L4-2350cc 2.4L SOHC (1992)
Fuel Filler Cap: Description and Operation
Fuel Filler Cap Operation
LOCATION
At the end of the fuel filler tube.
PURPOSE
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).
OPERATION
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.
