Triumph Repair: Triumph spitfire gas tank, canister, vapor

Question
I have a 1978 spitfire and i recently had the gas tank replaced. it drove fine and wonderful, but a few weeks ago i went to fill the tank and under the gas cap, where the nosle goes was gone. i assume into the gas tank since i have torn out the trunk and the back board of the car. What should i do. Also the gas tank was replaced because it was not venting correctly. I was looking the tank over and found a tube that goes to the carbon canister but is not connected to the tank but leads up to the tank as though it should be connected. If you could explain to me what is going on that would be great.

Answer
I am having trouble picturing what you state is "gone", as I thought most of the spitfire gas fillers were a solid piece.

If you believe something has fallen into the tank, the easiest solution would be empty the tank, remove it, and up end it to find your missing part.  You can empty your tank by removing the feed line from the carb and just run your pump (if an electric fuel pump) into a gas can(s) to get the majority of the fuel out.

The vent/vapor recirculation/collection system was always tied together; there should be barb fittings on the tank itself for the vent/canister connection; on the tank I remember, the connections were in the upper corners of the tank, but on the later emission versions, I believe they were on the neck of the filler as well.   All the lines should be connected according to the diagrams, which you can find in any of the triumph part dealers (Roadster factory/victoria british/moss) for your year.

The vapor/collection system was a series of plastic tubes that ran between the carbs and the storage/charcoal canister in the engine compartment, the gas tank itself, and an expansion/collection tank that sat inside one of the rear fender wells.  Its purpose was to collect gas vapors when the car was not running, and reintroduce those vapors when the car ran.

Hope I've helped