EVAP System (Evaporation Control)
This system is designed to prevent the release of gasoline vapors into the atmosphere. Although EVAP systems vary they all contain one similar component. This component is the Charcoal Canister. The canister is responsible for storing gasoline vapors from the vehicle's fuel tank/s and carburetor float bowl (if applicable) until the engine is ready to burn them through the combustion process.
Location: The charcoal canister is usually located in one of the far corners of the engine compartment. It is normally a black container filled with charcoal pellets that absorb fuel vapors. Not all charcoal canisters however are located in the engine compartment. Some vehicles manufactures have mounted their canisters closer to the vehicle's gas tanks in-order to maximize efficiency.
For the Smog Test: The state of California's BAR has started to perform the EVAP Functional Test, also known as the Low Pressure Fuel Evaporative Test (LPFET). This will be in addition to the standard smog emissions test. 1976 to 1995 model year vehicles will be tested, which includes all pre OBDII vehicles subject to Smog Check. The most important impact on consumers is that the emission reductions will improve air quality and reduce their health risks. This test is designed to insure your vehicle's fuel evaporative system is not leaking gas fumes in to the atmosphere. It is estimated that over 7,000,000 vehicles will need to be tested each year and of those 11% will fail. The average cost to repair a failed EVAP system is estimated to be approximately $250.00. Check your vehicle's "Underhood Emissions Information" label or with a certified smog repair shop for detailed location information. Find this component and insure it is connected properly.
Which vehicles are exempt from LPFET?
- Vehicles not originally equipped, and not required by state or federal law to be equipped, with a fuel evaporative control system.
- Dual Gas Tanks - Vehicles with two or more fully operational fuel tanks or gas tanks.
- Vehicles with fuel evaporative lines not accessible without requiring the vehicle to be partially dismantled to gain access.
- Vehicles powered exclusively by compressed natural gas (CNG), liquefied petroleum gas (LPG), or liquid natural gas (LNG).
In Case of Failure: In the unfortunate event that your vehicle fails the LPFET or EVAP test, you will need to seek repairs at a state certified smog check repair center. The entire EVAP system route will need to be traced. The system should consist of fuel vapor hoses running between the gas tank to the charcoal canister, through a purge valve and into the intake manifold. The smog technician will need to ensure that all hoses, solenoids and valves belonging to the EVAP system are connected and functioning properly. In most cases if a thorough diagnosis is conducted, the fault should be simple to find.
The only problem some smog repair stations have reported so far has been difficultly following certain EVAP hoses through the vehicle's chassis and areas not plainly visible. An expert repair station can deal with this issue.