What is evaporative emission control system?
An EVAP leak is a fault in the evaporative emission control system (EVAP). The evaporative emission control system function is to keep gasoline fumes in the fuel tank from reaching the atmosphere. This keeps air pollution down and keeps the smell of fuel from reaching the inside of your vehicle. Fuel vapors are emitted from vehicles any time there is gasoline in the tank. So if you have a leak, even if you are not driving the vehicle, those vapors are polluting the air 24 hours a day.
Is it Safe to Drive with an evaporative emission control system Leak?
'yes'. However, this doesn't mean that you should. The evaporative emission control system in your car serves to contain the fumes that are created by fuel in your tank. These fumes have to be prevented from getting into the atmosphere so that they will not contribute to the already-worsening air pollution. So, yes, you can still drive your vehicle safely as it really doesn't have a bearing on the overall performance of your car.
Why There Can Be Leaks:
A leak in the Evaporative emission control system can occur almost anywhere. It can be because of damage to the hoses that convey the gasoline fumes to the engine. As everyone knows, hoses are not exactly immune from damage. Over time, they can become brittle and form cracks where fumes can escape. It is also possible that one of the EVAP hoses has been disconnected, allowing the vapors to escape.
Another potential cause of a leak in the Evaporative emission control system is leaks in the charcoal canister itself. Again, these can degrade over time because of corrosion or exposure to impact forces. The canister itself can get cracked allowing vapors to hiss through the small opening. The canister can get severely damaged that your only recourse is to have it replaced.
Other causes of EVAP leaks can include faulty vent control valve or the purge valve. These valves can get stuck in their respective openings, too. When stuck, they will not be able to function normally and will not be able to purge the stored gas vapors into the engine's intake valve. It is also possible that there's a problem in the leak detection pump or any other leak in the car's fuel system.