Fuel Filler Cap: Description and Operation

Fuel Filler Cap:

PURPOSE
Seals fuel inlet, allows air to enter tank and vents excessive fuel tank pressure.

LOCATION
On the fuel filler inlet.

OPERATION
When vacuum develops in the tank, valve "A" opens to admit air and thus equalize tank pressure. When the fuel pressure in the tank is excessive the valve opens, allowing fuel vapor to vent to atmosphere.