what for the canister valve is used in the car? thanx
and if its not working properly hurts the car?

 

I am assuming you are talking about the purge canister. It is an emmisions device and it should be kept in working order. It is not a critical part, your car won't blow up or anything, but you might not pass emisions testing, its gonna cause a check engine light,and will throw reading to the PCM off.

 

It is a vapor recovery system much like the funky special nozzles we use today to catch fuel vapor and condense it in the charcoal canister and then use a purge solenoid to let fresh air in to pick up the fuel and suck it into the intake and burn it (only on part throttle these days). The fresh air attracts the fuel and rejuvenates the charcoal. This is why you should not over topoff you fuel tank as well as raw fuel will destroy the canister by oversaturating the charcoal. At this point you can fail emissions. Opps. Also you may get these codes if you fill up while the engine is running on slightly older cars. They could run vacuum tests at idle. Reset many a check engine light when wife left the engine run and filled up. New cars are now doing this almost exclusively at part throttle toavoid this problem. Hope this clears this up a little.

Basically your EPA at work.