Fuel tank venting system

A method of venting air to a fuel tank without allowing fuel vapors to escape to the atmosphere, comprising the steps of:

• providing a fuel cap having a valve cavity in a bottom thereof, said valve cavity having a substantially concave bottom, forming a flow passage through a top of said fuel cap to said valve cavity;
• inserting a diaphragm into said valve cavity, said diaphragm being fabricated from a flexible material having memory, a moveable outer perimeter of said diaphragm sealing said substantially concave bottom;
• and
• inserting a vent disc into said valve cavity, said vent disc including a diaphragm protection with a substantially convex surface on a top thereof, forming at least one air passage through said vent disc.

A method of venting air to a fuel tank without allowing fuel vapors to escape to the atmosphere, comprising the steps of:

• providing a fuel cap having a valve cavity in a bottom thereof, said valve cavity having a substantially concave bottom, forming at least one flow passage through said fuel cap to said valve cavity;
• inserting a diaphragm into said valve cavity;
• and
• inserting a vent disc into a bottom of said fuel cap, said vent disc including a diaphragm projection, forming at least one air passage through said vent disc, a moveable outer perimeter of said diaphragm sealing a bottom of said valve cavity, a vacuum in the fuel tank unsealing said diaphragm to provide air flow to the fuel tank through said at least one flow passage and said at least one air passage.