Evaporative Emissions System: Testing and Inspection

WARNING! These checks 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 properly designated area

- Be sure both valves are cosed when storing the tester.

Before checking, ensure the following:

- Fuel filler cap securely closed

- Fuel level 2/3 full (minimum), otherwise excessive pumping will be required to pressurize the system












- Disconnect the small hose from the carbon canister

- Connect slack tube tester US 4487 to the disconnected hose, ensure that tester is kept vertical

- Open both slack tube tester valves a half turn

- Zero the tester by moving the reference line even with the tops of the mercury columns

- Operate the hand-pump to pressurize the system to 1.3 inches of mercury

NOTE: If the system reaches the 1.3 inches of mercury soon after you start pumping, there is reason to suspect that the gravity valve or the hoses connected to it might be pinched or blocked. With 2/3 of a tank of fuel it should take considerable pumping to reach the specified pressure.







After pressurizing to 1.3 inches of mercury, wait five minutes and then read the pressure

- must be 1.2 inches of mercury or greater

If less than 1.2 inches of mercury

- check the fuel filler cap and vicinity for leakage using a soap solution,repair or replace as necessary.

- Re-pressurize to 1.3 inches of mercury and wait for five minutes

If less than 1.2 inches of mercury

- Disconnect the hose from the top of the gravity valve (between the gravity valve and the carbon canister) and seal off

- Re-pressurize the system to 1.3 inches of mercury and wait five minutes.

If less than 1.2 Inches of mercury

- The leak is between the gravity valve and the carbon canister .

If the pressure remains above 1.2 inches of mercury

- Reconnect the gravity valve and re-pressurize the system to 1.3 inches of mercury

- Check the hoses and hose connections for leakage at the expansion tanks and fuel tank using a soap solution

- Seal, repair or replace as necessary

After repairing any leaks

- Repeat the test to verify that all leaks have been discovered and repaired

- After the entire procedure has been satisfactorily performed, close both valves on the slack tube tester and properly store it away