The canister is meant to absorb fuel vapour from the tank when the car is not running, stopping it from entering the atmosphere. Shortly after starting up the solenoid opens and draws air through the caniste from the tank and its vent valve on the cap. Its all about emission control and sucking up those nasty petrol fumes. Personally id have a very good look for leaks in your fuel system especially as its right on top of the starter motor and coil. BBBBBBBOOOOOOOMMMMMMMMM!!!!!!!!!!!!
If it aint broke then dont fffffffix it!
My advice may not be worth much, but at least it's free!