C 2500 Truck 2WD V8-305 5.0L (1990)
Vapor Canister Altitude
^
Apply a short length of hose to the lower tube ("PCV") of purge valve and blow into it. Very little air should pass into canister if any at all. If the
canister has a constant purge orifice a small amount of air may go into canister. If air passes into canister, replace canister. If air does not pass into
canister proceed to next step.
Use a hand vacuum pump and apply 15" Hg of vacuum to the tube labeled "CONTROL VAC" on the purge valve diaphragm cover. The diaphragm
should hold vacuum for at least 20 seconds. If it does not replace the canister. If it does hold vacuum proceed to next step.
With vacuum still applied to the control vacuum tube, blow into tube labeled "PCV." If air flow into the canister increased, purge valve is OK. If air flow
does not pass into the canister, purge valve is bad and canister must be replaced.
TANK PRESSURE CONTROL VALVE
Tank Pressure Control Valve
Install a short piece of hose on the valve inlet tube (fuel tank side) and blow into the hose. You should feel the diaphragm pop open and air should pass
through the valve. If the valve does not open, it should be replaced.
