Fuel Tank: Description and Operation

Fig. 23 Evaporative Emission Control System, 1970-73 (typical):

Fig.24 Evaporative Emission Control System, 1974-76 (typical):

Fig.25 Evaporative Emission Control System, 1977-82 (typical):

PURPOSE
On early model fuel tanks, an integral fuel expansion tank, Fig. 23, is used to provide space for normal fuel expansion.

OPERATION
Fuel passes through small holes in the expansion tank at a given rate as fuel volume increases due to rising temperatures. Late model fuel tanks, Figs. 24 and 25, are designed with an expansion area directly above the fuel. Some vehicles with this type of fuel tank have a liquid check valve to prevent fuel from entering the vapor lines.