Evaporative Emissions System: Description and Operation

Fig. 452 - Evaporative Emission System:

This system--Figs. 452--is composed of a fuel tank with positive sealing filler cap, liquid/vapor separator, vapor vent line, and flow guide valve. With engine off, gasoline vapors are present in the vapor vent line, liquid/ vapor separator, and fuel tank. When pressure exceeds 0.4 in Hg, the flow guide valve causes this vapor to enter the crankcase. With engine running, vapors stored in the crankcase, manifold, and carburetor air cleaner are sucked into the manifold for combustion. When a vacuum is created by decreasing fuel level, the flow guide valve delivers outside air from the carburetor air cleaner to the fuel tank. The flow valve guide prevents reverse flow of blow-by gas from the crankcase.