I noticed that on my 89 2.8l, the charcoal canister has the line leading from the gas tank but the return line to the "TVS" is missing, just an open port on the canister. And where the return line is supposed to connect to the TVS, the chiltons guide shows 3 ports but my TVS has only 2. Does it really matter if theres vacuum applied to the canister?

 

I have my charcoal canistor hooked directly up to the throttle body. There is a 2 port "ported vacuum switch" on the intake area by the thermostat that is suppose to apply vacuum to the canister when the engine is hot. My switch is broken so I only bypassed the switched and have vacuum hooked up at all times to the canister. I guess the engine gets the fumes from the gas and maybe uses a little less fuel this way? Not sure if it HAS to be hooked up.