What does it mean?
The evaporative emissions (EVAP) system is used to prevent fuel vapors (hydrocarbons) from being released into the atmosphere. This is accomplished by trapping the fuel vapors in a charcoal canister when the engine is off. Once the engine is running, the vapors are purged from the canister into the engine and subsequently burned. The following components are used in the EVAP system: Charcoal canister This is the heart of the EVAP system – it traps and stores the fuel vapor.
The chemical composition of charcoal allows it absorb the vapors then release them when fresh air passes over. Fill Control Tube This is the part of the system that shuts off the gas pump nozzle when you your tank is full. It is located along the top of the filler neck and provides an expansion space at the top of the tank for fuel vapors. Gas Cap This is the part of the system everyone is familiar with.
What most people don’t know is that the cap contains a pressure relief valve, which allows the system to vent in the event of a malfunction. Purge Solenoid The purge solenoid controls the purge valve based on commands from the PCM. The PCM will typically command the solenoid on when the engine is warm. The vehicle also has to be traveling at a certain speed with the throttle open a specific amount. Purge Valve The Purge valve regulates the flow of fuel vapor from the canister into the engine.
Canister Vent Solenoid On vehicles with enhanced EVAP systems, the vent solenoid is used to seal the system off from outside air. This allows the system to perform its self-test for leaks. A typical EVAP system