Evaporative Emissions System: Testing and Inspection

Evaporative system leakage, troubleshooting

WARNING!
These tests involve the use of equipment that contain mercury.

Mercury is a toxic and hazardous material.
- exercise extreme care when handling
- do NOT allow to come in contact with eyes, nose, skin, etc.
- when not in use, store carefully in a properly designated area
- be sure both valves are closed when storing tester

Check these first
- fuel filter cap securely closed
- fuel level at least 2/3 full (otherwise it will require excessive pumping to pressurize the system)




- disconnect small hose from charcoal canister
- vertically connect slack tube tester US 4487 at disconnected hose from charcoal canister
- open both slack tube valves a 1/2 turn
- move scale on tester such that the zero line is even with the tops of the mercury columns





- pressurize the system to 1.3 inches of mercury, using the hand pump

NOTE:
If the system reaches the 1.3 inches of mercury soon after you begin pumping, there is reason to suspect that the gravity valve or hoses to it, might be pinched or blocked.

With 2/3 of a tank of fuel it should take considerably more pumping to achieve the 1.3 inches of mercury.
After reaching 1.3 inches of mercury on scale, wait 5 minutes:
- system OK if pressure is 1.2 inch of mercury or greater

If pressure drops below 1.2 inch of mercury:
- check fuel filler cap for leakage using soap solution, replace if necessary
- pressurize system to 1.3 inches of mercury, wait 5 minutes

If pressure still drops below 1.2 inch of mercury:
- disconnect hose from top of gravity valve (between gravity valve and charcoal canister) and plug hose
- pressurized system to 1.3 inches of mercury, wait 5 minutes

If pressure still drops below 1.2 inch of mercury:
- the leak is between the gravity valve and charcoal canister

If pressure does NOT drop below 1.2 inch of mercury:
- reconnect gravity valve and re-pressurize system
- check hoses/connections at expansion tanks and, fuel tank by applying a soap solution
- seal, repair or replace as necessary

After you have repaired the leak(s):
- repeat test to verify that you have fixed all of the leakage
- after tests are completed, close both valves on the tester then properly store