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 (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 (including a loose or missing gas cap); it will set a fault code and turn on, the check engine light.

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

The most common problem, with the (EVAP) canister 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 combustion process, when necessary.

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 and cause the canister purge valve, to stick in the open or closed position.

Finally, the (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 be illuminated.


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 Control 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


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