Light Duty (GVW 8501 LBS or More)

SYSTEM SERVICE

Ensure all vacuum hoses and electrical wires are routed clear of the exhaust manifold to prevent deterioration due to the high temperature. Vacuum hoses should always be a minimum of three inches from the exhaust manifold.
NOTE: Use only fuel resistant hoses when servicing the evaporative control system.


CHARCOAL CANISTER

The charcoal canister is a sealed service-free unit. The canister control valve can be checked by disconnecting the 3/16 vacuum hose on the canister and connecting a vacuum source in its place. If the control valve cannot hold 10 inches of vacuum, the canister must be replaced.


ELECTRIC [1][2]BOWL VENT VALVE

Follow the following steps to determine if the electric [1][2]bowl vent valve is functioning properly. If none of the following conditions exist, the electric bowl vent valve should be replaced.
1. Disconnect the vacuum hoses from the valve and the electrical connection from the wiring harness.
2. Place a 1/8" vacuum hose on the carburetor bowl side of the valve. With the valve completely disconnected from the system, you should be able to blow through the valve and feel air exiting through both ports.
3. Connect battery voltage to either side of the valve and ground the other side. A click should be heard as you apply and remove the ground from the valve.
4. Reinstall the valve into the system, except the 1/8" vacuum hose on the carburetor side of the valve, and start the engine.
5. Blow through the 1/8" hose and air should come out the port that goes to the air cleaner, and none should come out of the port to the charcoal canister.



VAPOR CONTAINING AIR CLEANER ASSEMBLY

TEST PROCEDURES (DELAY VALVE)
1. Remove the vacuum supply hose from the vapor containment door vacuum delay valve.
2. Connect auxiliary vacuum supply to delay valve.
3. Apply 15 inches Hg of vacuum.
4. Release vacuum.
5. Vapor containment door should open when vacuum is applied and close within 40 seconds when vacuum is released.

TEST PROCEDURES (VACUUM DIAPHRAGM)
1. Remove vacuum supply hose from the vacuum diaphragm on the air cleaner snorkel.
2. Connect hand vacuum pump to the vacuum diaphragm and apply 15 inches Hg of vacuum.
3. Release vacuum.
4. Vapor containment door should open when vacuum is applied and close when vacuum is released.

DIAGNOSIS
1. If door does not close within 40 seconds when vacuum is released, replace the delay valve.
2. If door does not open when vacuum is applied, verify if the problem is the delay valve or the vacuum diaphragm. Replace the faulty component.