1985 Spectrum with fuel dripping?

I am trying to keep my 85 spectrum going and need some diagnostics help.
It is a carburated model, has 46K miles and is in great shape except it is dripping fuel on the driveway and I am not real familiar with the black canister that is mounted on the firewall.
It has a hose that appears to be an overflow tube that goes into the chassis above the front drivers side A frame. I have a steady drip of fuel and don't know where to start.
I can't afford to take it to the dealer or repair shop but I can change parts myself if I can figure out what is causing this.
It has been a great little car but like me it is getting old and needs a doctor.

This canister contraption has tubes comming and going from both the top and bottom and some sort of valves or sensors in the top.
I am assumeing there is a clog or air/vaccum leak or one of these sensors is not shutting off. Reminds me of a float needle being stuck but I don't know if it even has one of these.
I took it to the dealer in November for this problem and they replaced the gas cap and charged me $81.00. It did stop the drip but it is now back and I just don't have that kind of money.

Can anyone give me some pointers here for what to change to stop the drip?

Thank you.

Gary

The black canister is a vapor canister. Someone will correct me if I am wrong but they simply just collect fuel vapors from the tank and store them to burn them later. When I put the new edlebrock carb on my 86 k10 I just got rid of the canister and plugged the lines. Your fuel leak is probably just that, a leak. Try to see where it is coming from, may have a hole in one of the lines going to the canister.

Thank you Abaird. I know you are right about the canister being and evaporator but I just don't know the working of the system.
The drip I have is deffinately comming from an overflow tube out the bottom of the canister which is telling me something is either plugged or has lost vacumm preasure or one of the valves is not functioning propperly.

I did get fuel in a full service place not long ago and the attendent got carried away trying to fit more then necessary into the tank. I am wondering if in overfilling it he could have filled the vent tube with liquid and screwed up the function of the system so no air will go thru.
Could be as simple as blowing out the vent tube and allowing it to breath or as painfull as replacing all the purge valves and lines to find the offending part.

I was hoping for some advice from members who have had this or similar problems and might have found the culprit before resorting to expensive part replacments or complete bypass of this system.

Gary