Fuel Filler Cap: Description and Operation

FUEL FILLER CAP






NOTE: If a fuel tank filler pipe cap requires replacement, use only a fuel tank filler pipe cap with the same features. Failure to use the correct fuel tank filler pipe cap can result in a serious malfunction of the fuel system.

The fuel filler cap (1) used on the FWD 1.8L engine is an interrupted thread design with a pressure-vacuum type operation. This type of cap requires only one quarter turn in order to seal the fuel system. A built-in torque limiting device on the cap prevents overtightening and also eliminates the escape of fuel vapors. To install the cap, turn the cap clockwise until a clicking noise is heard. This indicates that the fuel filler cap gasket (2) is fully seated.

The fuel filler cap (3) used on the AWD 1.8L engine is an updated version of the screw thread design. This latest version of the screw on cap provides only one click with a firm stop, when the cap is correctly installed. Tightening the fuel cap until the one click is heard assures a sealed fuel system. The fuel cap is a pressure-vacuum type operation. To install the cap, turn the cap clockwise until the cap stops and the one click is heard. This indicates that the fuel filler cap gasket (2) is fully seated.

A vacuum relief valve is incorporated into the fuel filler cap. If the pressure in the fuel tank becomes negative (vacuum), the relief valve opens to relieve the pressure created within the fuel tank. Only when the vacuum becomes excessive within the tank does this occur. Vacuum pressure is also vented through the tank pressure control valve which is located on the top of the fuel tank.

A pressure relief valve is also located in the fuel filler cap. The pressure of the fuel vapor within the tank should exceed that for which the fuel system is designed, the pressure relief valve opens, and the excess pressure is vented to the atmosphere.