Evaporative Emissions System: Testing and Inspection

Fig 34 Manometer Fabrication Dimensions:

CAUTION: Fuel vapors are extremely flammable. Do not smoke or use an open flame in area during test.

1. Inspect carburetor for proper external bowl vent operation an possible flooding.
2. Inspect air cleaner and if equipped, trap door mechanism for proper operation.
3. If equipped, inspect fuel return pipe.
4. Inspect engine compartment for any obvious fuel leakage onto or near power train components and exhaust system.
5. Weigh fuel vapor canister. If it weighs more than 2.5 pounds, replace it.
6. Start engine and check for the following conditions:
a. Erratic engine operation due to air leakage into vacuum hoses especially at the canister. Repair as necessary.
b. Fuel leakage from any high pressure pipe fitting located between fuel pump and filter, and between fuel filter and carburetor. Repair as necessary.
7. Turn engine off and test integrity of fuel vapor control system as follows:
a. If a manometer is not available, fabricate one according to Fig. 34. Attach a 6 foot length of 3/5 inch clear plastic tubing to a 4 foot x 6 inch x 1 inch board.
b. Fill tube with water to a height of 15 inches.
c. Visually inspect fuel vapor control system for loose or damaged hoses, clamps etc. Repair as necessary.
d. Inspect fuel filer neck sealing surface for scratches and dents. Small dents and scratches may be removed by sanding entire surface with sand paper. If dents or scratches are severe, replace fuel filler neck.
e. Disconnect fuel tank vapor hose from canister at engine compartment and apply pressure to make sure hose is not obstructed.
f. Using a tee fitting, connect plastic tube or rubber hose between manometer and fuel tank vapor hose. Make sure that fuel tank is no more than 3/4 full.

CAUTION: Do not pressurize system more than 1.5 psi (41.5 inches of water) in the following step.

h. Connect a hand pump to open tee fitting and pressurize system until column of water in manometer rises 15 inches from no pressure level.

CAUTION: Fuel vapor is highly combustible, do not smoke or use an open flame in area during test.

i. Inspect all fuel lines, hoses and connections for leaks indicated by stains, liquid fuel and bubbles. Repair as necessary.
j. Using a soap and water solution, test all system connections for vapor leaks as indicated by bubbles. Repair as necessary.
k. Check for fuel odor at fuel filler cap. Replace cap if odors are' detected.
8. Relieve pressure in system by slowly removing fuel filler cap and connect fuel tank vapor hose to canister.