System Diagnosis - High Altitude

INSPECTION


INCORRECT OPERATION MAY CAUSE:

^ Poor idle, stalling and poor driveability, check for:

- Inoperative bowl vent valve
- Inoperative canister control valve
- Damaged canister
- Hoses split, cracked or not connected to the proper tubes.


^ Evidence of fuel loss or fuel vapor odor, check for:

- Liquid fuel leaking from fuel lines, fuel pump or carburetor
- Cracked or damaged canister
- Inoperative canister control valve
- Disconnected, misrouted, kinked, deteriorated or damaged vapor hoses, or control hoses
- Bowl vent hose misrouted
- Air cleaner or air cleaner gasket improperly seated.

MAKE A VISUAL CHECK OF CANISTER
^ Visual check of charcoal canister
- Cracked or damaged, replace canister.
- Fuel leaking from bottom of canister. Replace canister and check operation of total system.
- Check filter at bottom of canister. If dirty, plugged, or damaged, replace filter



FUNCTIONAL TEST

Vapor Canister Altitude:

^ Apply a short length of hose to the lower tube ("[1][2]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 "[1][2]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.