What's the prurpose of the charcoal canister?

[aaronoverholser]

I have just completed a complete emissions removal via the Rotary Resurrection instructions. There is a cylindrical caniter on the pass. side of the engine compartment that I believe is called the charcoal canister. It has two lines running to it, one came from the engine block and was capped off in the directions. The other line is smaller and runs to a connection on the drivers side that goes under the car.


Can I do away with the charcoal canister?
What is it's purpose?
And if I do away with it what should become of that small line?


Thanks for your help, always wanting to learn!

[aaronoverholser]

Ohh, and this is on an 86 N/A GXL.

[FC Zach]

It filters the gasses emitted from the fuel tank.

[FerociousP]

the only reason to get rid of it is space and cleanliness. It is there to take the pressure built up in the fuel tank from gas vapor, and sort of filter them and allow them to go into the engine at some point. You don't want to cap off the vent from the tank, but you also don't want to leave it open really because you will get a gas smell sometimes...

with that said... I have mine uncapped. I don't necessarily recommend you do the same thing. Its technically illegal (comprimised vehicle emissions system).

[FRED]

.

[My5ABaby]

Although the RR write up is excellent, I would strongly recommend against removing and blocking off the BAC. There is absolutely no reason to do so. It helps your car maintain an idle when accessories are being used (i.e. power steering and A/C) and nothing is gained by taking it off.

"... when engine is stoped"

:rofl:

[Pete_89T2]

I would leave the charcoal canister alone; removing it buys you nothing WRT more power or reliability, but doing the bypass will result in a stinky fuel vapor smell under the hood. It doesn't weigh all that much or take up too much space, and since it's a passive device it's very reliable - I've never heard of one these things failing - ever.

These "evaporative emissions" systems have been in cars in the US since the late '60s/early 70's. Before that time, gas tank caps simply vented straight to atmosphere, allowing any fuel vapor pressure that builds up in the tank to escape. To reduce pollution from those gas vapors, the automakers changed the gas caps to sealed designs that don't vent. Your FC has a sealed gas cap. To deal with the vapor pressure that still builds up in the tank, they plumb it to the canister for what amounts to temporary storage. When your car is running, the line that connects to the engine will suck any built-up vapors stored in the cansiter into the combustion chambers to be burned. When the car is NOT running, the volume of the canister alone is typically sufficient to trap all the vapors your fuel tank produces, BUT if it's hot OR the gasoline in your tank has a higher than usual vapor pressure, that's where the charcoal comes into play.... The charcoal absorbs most of the hydrocarbon molecules present in the fuel vapor, allowing the excess pressure to safely vent to atmosphere minus the hydrocarbon pollutants and that stinky fuel smell. Think of it as a chemical one-way check valve.

[aaronoverholser]

Thanks guys. I guess I will leave it in the car!

[Raksj04]

but what if one of the nipples break? I had a gas smell coming from under the hood and it turns out the nipple cracked on the feed side. I googled the part number and the Mazda OEM online stores want $125 ish for a new one.

[Pete_89T2]

but what if one of the nipples break? I had a gas smell coming from under the hood and it turns out the nipple cracked on the feed side. I googled the part number and the Mazda OEM online stores want $125 ish for a new one.

You may be able to repair the cracked nipple with epoxy. If not, just find a replacement part in a junkyard. These things rarely break or go bad, don't need to buy a new one.

[RETed]

No need to resurrect this thread, when you started another one.
I'm closing this one.
PM me if anyone has a good reason to open this thread back up.


-Ted