The first thing in order, we need to differentiate between the charcoal can and the vapor canister. The charcoal can is on the trunk wall and looks like a black coffee can. The vapor canister is mounted next to the air box on the strut tower (On the V6 I know, I'm unsure of where it's at on the four cylinder... Same place maybe, I don't know.) You talking about the fuel vapor canister I know, but for those newbies out there
Charcoal Can: This is used as a vacuum reserve for the engine and its accessories, like cruise control. The engine basically just pulls a vacuum on the can so that there is extra vacuum if the motor cuts off or the like. As long as the rubber lines running into it aren't crimped, it really doesn't matter where its mounted, or at what orientation (up, down, sideways, hanging from the lines
Fuel Vapor Canister: This can pulls excess fuel vapor from the expansion tank (from the fuel tank on pre 87 models IIRC). A regulated vacuum line opens the dyaphram on the top of the canister and circulates the vapor back into the plenum. In theory, it shouldn't matter what orientation this can is mounted at, as long as its mounted at a realitivly high point compared to the gas tank. The vacuum should pull the gas upward if needed, but it would be bad to get pockets in the line if it were below the gas expansion tank. I wouldn't second thing mounting it sideways.
Later model Vapor canisters are rather large, about twice the diameter of the Fiero Vapor canister.
|Originally posted by DEMONCHILD:|
are they even necessary?
Yes they are needed to vent the gas tank of excess gaseous buildup, which could be dangerous.
Hope that's everything.