Hot Engine System Test

Fig. 72 Checking Vacuum To The Purge Control Valve:

NOTE: The engine should be at its normal operating temperature (the cooling fan should cycle on and off at least once).
1. Disconnect the #19 vacuum hose at the purge control valve, Fig. 72, and connect a vacuum gauge to the hose.

Fig. 73 Checking Flow Of Charcoal Canister:

2. With the engine at idle, vacuum should be available. If no vacuum is available;
a. Disconnect vacuum hose #18 at thermovalve A, and check for vacuum (with engine at idle).
b. If there is no vacuum, check the routing of hose #18, check all hose connections for cracks or leaks, check all vacuum orifices for blockages and repair as necessary.
c. If there is vacuum, replace thermovalve A, and re-test.
d. Disconnect the vacuum gauge and re-connect hose #19.
3. Charcoal canister test.
a. Remove the fuel tank filler cap.
b. Remove the canister purge air hose from the frame and connect the hose to a vacuum gauge, Fig. 73.
c. Raise the engine speed to 3500 rpm. Vacuum should be available within 1 minute.
d. If vacuum is not available, remove and inspect the charcoal canister for signs of damage, and replace as necessary. If the canister is not damaged, test the purge valve.
e. Stop the engine, disconnect the vacuum gauge, and re-install the filler cap.

Fig. 74 Checking Charcoal Canister Purge Control:

4. Purge valve test.
a. Disconnect the hose from the charcoal canister PCV fitting, Fig. 74.
b. Connect a vacuum pump to the canister purge fitting and apply vacuum. The vacuum should remain steady. If the vacuum drops, replace the charcoal canister and re-test.
c. Start the engine and reconnect the vacuum hose to the canister PCV fitting. Purge side vacuum should drop to zero.
1. If purge side vacuum does not drop, replace the charcoal canister and re-test.
2. If purge side vacuum drops to zero, connect a vacuum pump to the PCV fitting on the canister and apply vacuum. If vacuum drops at the PCV fitting, replace the charcoal canister and re-test.

Fig. 75 Checking Charcoal Canister:

d. Connect a vacuum pump to the tank fitting on the charcoal canister and apply vacuum, Fig. 75. If the tank fitting holds vacuum, then the canister is blocked, and should be replaced.