Basically, there are no two ways about this: You can't install the fresh air fan and vent ducting system without installing the fuel tank and the evaporative emissions control system at the same time. There are a couple of steps that dovetail between the two installations and it all takes place in the close confines of the trunk. In addition to that, make sure all of your knobs are in place and that you've installed the dash-mounted ashtray. After the fact, it is nearly impossible. Not surprisingly, there isn't a wealth of information regarding the evaporative emission control system on the 1970 and later Beetles, except for the general explanation in the Bentley book and a short how-to about fixing a fuel leak at www.superbeetlesonly.com. Other than that, you're really on your own, and hopefully you took a bunch of before pictures when you tore your Super down to a shell. You didn't? Oh, well, don't worry because we did.
In short, the emission control system consists of an expansion chamber that is connected to the tank that collects overflow gas from a full fuel tank. It is stored in this tube under the cowl until the fuel level eventually drops. In addition, the evaporated fuel from the tank (after the engine has been shut down) is forced up through the expansion chamber and into the ventilation lines. Then those fumes travel to the rear of the car where it is "washed" in an activated charcoal canister. The charcoal absorbs the vapors and, when the engine is restarted, the cooling fan blows the trapped vapors into the carburetor where the engine burns them off.
Sure, it sounds simple, but the complication of tubes, hoses and connections can challenge the patience of any builder. Because of this, we built and rebuilt the systems a number of times because there is a certain order of assembly. In addition to this, we realized that a lot of the parts needed aren't currently being produced, which makes for a difficult installation if your car is missing something.
A note about safety: We've said it before and we'll say it again, there's nothing more final than fire. Old gas tanks, even if they seem empty, still contain vapors, and vapors plus an errant spark or a buildup of static electricity can cause a large explosion in a flash. To combat this, always disconnect your battery and ground your car. Keep a fire extinguisher handy, however.
On the other hand, there's nothing remotely hazardous about the fresh air/heating ventilation system and you shouldn't worry about anything besides making aftermarket parts fit with OEM parts on original parts. Oh, but that's part of the fun, right?
Let's just get started.
Conclusion:Some of the details needs to be addressed. For example, we didn't connect the trunk release or the fuel door release levers. As well, we'll need to re-install the correct fan shroud with the flange to accept the charcoal canister hose, and later we'll add to the system the water canister and lines for the winshield wipers, and consider replacing the jack.
If you smell fuel inside the cabin or inside the trunk, you've got a leak somewhere. Either you haven't used brand new fuel lines or you've got a component that no longer holds its integrity. Sometimes, the expansion tube and charcoal canister (which are no longer offered) don't work and must be accounted for. If that's your problem, you must reroute some lines to block of these two things. Avoid any leaks at all costs. In reality, a 1971 Super doesn't have to pass smog tests, and because of that, it doesn't have to be environmentally sound. Converting your tank from this complication of tubes and hoses to that of an earlier system is simple: Merely connect a hose from the filler neck to the top left corner of the tank and connect together the two inlets on the upper right side of the tank, therefore bypassing the charcoal canister system and lines and the expansion chamber. For more information on this change, check out www.superbeetlesonly.com.
Next month, we're going to take you through the installation of the hoods and fenders, the chrome trim, bumpers, brackets, turn signals and lights, essentially, everything on the outside of the car. Until then, stay Super.