So, to prevent harmful gasses, escaping into the atmosphere, the evaporative emission control (EVAP) system, was the answer.

 Consequently, it is just one, of the many emission control systems, used to minimize the effect, of global pollution.

It is a fairly simple system, but needs to work flawlessly, to avoid other problems. The first goal, was to seal the system, preventing vapors from escaping.

So, to make the evaporative emission control (EVAP) system work, they had to come up with a, new fuel cap.

This new cap is what, actually seals the system. As a result, it is common to hear, “you may have a faulty or loss gas cap”. Now, what do you do, with all those captured fumes. When the fuel tank pressure, becomes excessive, a charcoal canister soaks up and stores the fumes.

The evaporative emission control (EVAP) system, usually requires no maintenance. Newer vehicles can run diagnostic self-checks, to detect fuel vapor leaks in the system. Then, if it finds any leaks, it will set a fault code and turn on, the check engine light. (including a loose or missing gas cap).

Now, when it comes time to empty the canister, this is where the magic happens.

The most common problem, is a faulty purge control or vent solenoid.

The canister purge valve, allows stored fuel vapors in the containment canister, to be recycled back into the engine.

As a result, the canister purge valve, seems like the weak link in the system. It is not uncommon for bits of charcoal to separate from the charcoal brick, inside the canister. As a result, causing the canister purge valve, to stick in the open or closed position.

Finally, the evaporative emission control (EVAP) system is a network of, hoses, valves, filters and more. Consequently, issues with the (EVAP) system, are in the top 5 reasons, for a Check Engine light to come on.

Choose Your Help  Topic Below

Evaporative Emission Control System (EVAP) – Function – Failure

Automotive Emission Control Systems – Must Perform One Important Job

Check Engine Light (CEL) – What Can Cause It To Come On

Loose Gas Cap – Evaporative Emission System (EVAP) Self Test

Fuel Leaks – If you smell gas, this could be a sign of a fuel leak.

Engine Problems – What Are The Most Common, Engine Problems

Thank You !