Replace the evaporator?
 

I've been having constant gas fumes in the cockpit in my '74, especially after fill-up. I removed the pan, tightened up the lines, and scoured the car for visible leaks. Everywhere is dry and smells clean except the cabin and the smugglers box (the fuel sender gasket is not the issue). I did some research on the board and think it may be the evaporator.

Since I'm new to the 1974 911, where is the evap. on my car? Does a bad evap. coorespond to the fumes I smell coming from the smugglers box and the cockpit? Any other ideas on where to look?

I've had the same problem on my 1987. I replaced the fuel lines to the tank and that seems to have solved the problem. Check the plastic overflow "bottle" for leaks. Another solution may be to not top up the tank when filling it.

the evaporator is located in the smuggler's box..plot thickens..
ryan

Maybe you need to check the gas tank for visible rust. The thank may be have a very little leak. Or the fuel sender gasket is not sealing properly. Check for lose or broken fuel lines in the the trunk.

The evaporator is an air conditioning component. I think you may mean something to do with the evaporative emission system. It is a smog control system to reduce gasoline fumes evaporating into the atmosphere. I can,t remember the setup on a 1974 but check for gas tank vent hoses going to some sort of overflow container.

shouldn't have emission controls on a '74..the a/c evaporator assembly contains an electric fan to blow air..could be blowing gas fumes from the adjacent fuel tank, but i'd have to look at my setup to see how it could happen.
ryan

The 1974 US spec cars certainly had a variety of emission equipment on them.California had emission regs as far back as 65 and 68 countrywide. The exact strategy for control I forget for each year and model. There has to be some tank venting anyway and the hoses usually directed the fumes from the top of the tank into some sort of container. I just looked up the exploded diagram for tank ventilation on theis site and there is a collecting fume tank piped from the top of the tank .

If it is the tank, how do I seal the "leak"? Is POR-15 tank sealer the best choice?

I also looked at the the tubing and tanks in the left front fender - it all seems ok with no smell. The only signs of fumes leaking, that I can tell, is coming from the smuggler's box.

I just now remembered what may be an important piece of info - Once the tank gets to around a 1/4 full, the gas smell decreases quite a bit. Could that be a leak higher on the tank?

This whole deal is starting to sound like a huge can of worms....

I would examine the tank for a leak at the area where it lays on the mounting edge. Tanks often develop leaks there from dirt and moisture trapped under the edge of the trunk floor and tank mounting lip.