OBDII - Components - EVAP System

EVAP System

- Last Edited: Aug 27, 2023
- Popularity: 1,010 Views


The Evaporative Emission Control System (EVAP system) is an integral part of a vehicle's emission control system. Its primary purpose is to prevent the release of fuel vapors from the fuel tank and fuel system into the atmosphere, as these vapors can contribute to air pollution and smog formation.

Here's how the EVAP system works:

1. Fuel Vapor Storage: As the vehicle's engine runs and the fuel heats up, gasoline can vaporize. Instead of allowing these vapors to escape into the air, the EVAP system collects and stores them in a charcoal canister or an equivalent component.

2. Purge Control: When the engine is running and certain conditions are met (such as specific engine operating conditions or time elapsed since the last purge), the Engine Control Module (ECM) or Engine Control Unit (ECU) commands the EVAP system to open a valve called the purge valve. This allows the stored fuel vapors to be drawn from the canister and into the engine's intake manifold. The fuel vapors are then burned along with the air-fuel mixture in the combustion chambers, reducing emissions.

3. Leak Detection: The EVAP system also includes components that monitor for leaks in the fuel vapor system. If a leak is detected, it can trigger a warning light on the dashboard (such as the "Check Engine" light) and the ECM/ECU can log an error code to help technicians diagnose and repair the issue.

Overall, the EVAP system is designed to capture and control fuel vapors to minimize their impact on the environment and to comply with emission regulations. It's an important part of modern vehicles and contributes to reducing harmful emissions from vehicles on the road.