First off, Since 1971, all U.S. vehicles have had fully sealed fuel systems that do not vent directly to the atmosphere (from wiki) These evap emission components have been around for 43 years! The charcoal canister stores the gas vapors whenever the engine is not running. The canister is purged when the engine is running, sometimes through the PCV valve's hose, and sometimes through a control solenoid depending on year, make and model, engine displacement, etc.
So what exactly is your problem? have any codes been gathered? and year, make, model please!
The evap system is made up of numerous parts.Gas cap,vent valve(on top of gas tank)long vacuum hose(from vent valve to vapor canister in engine bay area)vapor canister,purge valve,vacuum hose(from purge valve to intake manifold vacuum fitting)The purpose for the evap system is to vent fuel vapors from the tank and send them into the intake so they can be burnt by the engine.The gasket on the gas cap may be leaking or the vent holes in its edge may be clogged.OR the vent valve may be clogged or its grommet leaking.OR the long or short vacuum hoses may be leaking or clogged.OR the vapor canister filter may be soaked with fuel.OR the purge valve is malfunctioning.It should click when you turn the key on.A vacuum pump with gauge can be used to check the purge valve.The valve should open and allow intake manifold vacuum to draw in these fuel vapors to be consumed by the engine.A strong fuel odor is another sign for a defective purge valve.Vacuum leaks are the main cause for evap problems
Any car after 1996 has one, some before. If the code is for the purge valve, it probably needs a purge valve. If it is for a "gross leak" it might need a cap, or a valve, if it is for a small leak, it needs to be smoke tested
Replaced the gas tank filler tube on one car (a GM). Replaced the purge valve on another (Toyota). Wasted money on a gas cap on the first one. Don't believe everything you read on the internet. Maybe not even this, just kidding. It is best to search for the issue and your make and model of car, it may get you closer. It can take some scrutiny of the vehicle to find the leak or problem.
I don't know if by replacing my gas cap would help like it said on the interernet. I would be very thankful if someone would tell me if they have had that problem and what they did. I have put so much money in my car and am hoping its a simple solution. Any help would be appreciated
