Outlet and Inlet Valves

The intake (or inlet) valve permits a fluid or gas to enter a chamber and seals against its exit. The outlet valve works just the opposite; permitting the pressurized fuel to flow out into the fuel lines to the carburetor. A check valve above the fuel pump in the fuel line keeps the fuel from flowing back into the fuel tank when the engine is shut down. If this valve were not there, fuel starvation on start-up might occur, since it takes longer for the electric fuel pump to get up pressure in the fuel line than it does for a positive displacement mechanical pump.