R 2500 P/U 2WD V8-350 5.7L (1987)
Fuel Tank Pressure Release Valve: Description and Operation
Fig. 73 Fuel tank pressure control valve. 1987 V6-262, V8-305, 350 & 454 high alt.
This valve, Fig. 73, is used on 1987 high altitude V6-262, V8-305, 350 and 454 fuel injected engines. This valve allows fuel tank vapors to enter the
Evaporative Emission control system. When fuel tank pressure exceeds the calibrated spring pressure on the valve diaphragm, the valve will open
allowing fuel vapors to flow to the canister or directly to engine.