Not_An_Abba_Fan
Exhaust Guru
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to go into more detail;
its your carbon cannister. whether you need it or not is up to you. however it does serve a purpose.
when your fuel tank is cold, everything is fine. but if you hit a 30 degree day the fuel in your tank expands and needs to escape. the main place it will escape from is your filler neck (where you fill up with fuel) and on older cars on hot days you can actually see fuel vapour evaporating from the neck.
now here is the tricky bit. wet petrol isnt really that flammable. dudes in the movies drop cigarettes in petrol and WHOOSH up it goes... but its all bull. the stuff you wanna avoid is fuel VAPOUR. that stuff WILL go up with a bang.
what the cannister does is filter the fuel vapour and turn it into O2 and water (the hose out the bottom drips the leftover harmlss stuff) so when pressure builds up in your tank, rather than escaping out the filler neck it goes to the cannister and filters... thus making your flammable wreck a lot safer.
having said all that i took mine off and plugged the hoses cos its ugly., LMAO.
Yes and no. One thing that is incorrect is the turning into O2 and water part. The charcoal canister contains activated charcoal and the fuel vapours adhere to this. When the engine is started the vapours are drawn into the engine and burnt through the purge valve. If there is any water in there it is only condensation from the tank that has evaporated and has been taken along for the ride witrh the fuel vapour.
The other thing that is incorrect is seeing the vapour escape from the filler neck. The fuel system is completely sealed and if you see any vapour around the filler neck you have either a faulty fuel cap or breather hose.
You will see fuel vapour on older cars as they have vented caps. Post '73 ( I think) have sealed caps and charcoal canisters.