how does the evap work?

The EVAP emission control system basically sends gasoline fumes to the engine to be burned up instead of being released into the atmosphere. There's a few vacuum hoses, solenoids, and a charcoal canister involved. The computer regulates the flow and frequency of these fumes from the gas tank to the engine by opening and closing the purge valve. When the system has a leak the computer will turn on the check engine light or service engine soon light and a trouble code will be set. If a small leak is detected a smoke machine may be needed to find the leak. Smoke is injected in the system. Then the mechanic looks at the EVAP system lines carefully to see where the smoke is coming out. When they find the smoke, they've found the leak. Hope that helps! Jim