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Sat Oct 07, 2006 3:30 pm

So, what's the deal with these things?

I believe they are for smog control - to recover vapors from the fuel tank while letting the fuel tank breathe so as gas is consumed it's not creating a vacume, right? So, here's my guess as to the original setup:

Gas tank, to a small tube that goes to a T in the front boot - one end of the T goes into the lower connection of canister #1, the other side of the T goes...? (In my car, the other side is open to the boot, and makes the whole car smell of gas after I fill it up).

From canister #1, there's a small plastic/rubber/metal line that snakes through the car following the pan on the right-hand side. This feeds in to canister #2 that lives next to the starter. (on my car, that tube is cut, broken, and rotted in several places).

Canister #2 also has 2 larger pipes that go into the engine compartment. 1 connects to the fan shroud (presssurized air) and the other connects to the oil bath air cleaner (vacume). I assume this allows air to move through canister #2 whisking away the fumes into the intake to be burned with the real gas. Also, this probably gives a slight positive pressure to the entire system - possible even to the fuel tank. (on my car, both tubes have rotted and I have neither the original shroud, nor the oil bath cleaner - the only thing I could hook this to would be the breather box).

So, on my car, this system doesn't do what it did. But I'm not sure what it did do, and I'm not sure if it's at all important to me anymore. This is coming to a head as I'm looking for a place to mount my new electric feul pump - that tube that runs between the two canisters is right exactly where I want to mount it, and I'm thinking of just pulling the tube out.

Should I just cap it off? Should I just let canister #1 vent to the air? Should I fix the line, then let canister #2 vent to the air? Should I try to feed this back into the carb and not worry about positive pressure? I'm not sure where I can get positive pressure from in the engine compartment - the new engine uses a DTM shroud. It's not getting smog inspected anymore, but if simply hooking up the hoses cuts back on pollution, I'm all for it.

Mon Oct 09, 2006 11:00 am

The tee has two inlets, one comes from the filler neck and the other comes from the top of the drivers side gas tank where there should be a nipple. Braided vac hose runs up to the tee which should be at the top of the luggage compartment down to the expansion chamber on the drivers side. Then a clear tube runs underneath the tank and into a metal line that runs across to the passenger side of the vehicle and out to underneath the rear pass side wheel where it connects to the charcoal cannister. The charcoal cannister the has two hoses one from the top of the fan housing and the other goes into the air cleaner. All of these are to allow gas fumes to get burned up when the vehicle is running. These hoses also are a vent for the gas tank so make sure if you decide to remove the system to make sure you still have a vent running up to the top of the luggage compartment and then back down and out underneath the vehicle like an old bug or you will get vacuum on your gas tank which will limit gas flow and actually suck the sides of the tank in extreme cases.

Mon Oct 09, 2006 11:10 am

74 Thing wrote: The tee has two inlets, one comes from the filler neck and the other comes from the top of the drivers side gas tank where there should be a nipple.

Ah! Thanks! I don't have the original tank, and I've been told it's missing at least one of the hookups - what you describe isn't on the tank.

It sounds like the quick-and-easy answer is to cap off one end of that T, leave the connection to the forward canister, then perhaps just let it vent at the ground where the hose is rotted out.

Mon Oct 09, 2006 12:23 pm

Yeah that is how the old bugs did it-they ran the vent tube up high and then back down and underneath the tank to vent to the ground. Just be careful if you decide to replace all of the tubing and run through the metal lines to the rear charcoal cannister, first check to see if the metal line has rusted shut. Mine rusted shut and I did not catch it so it created a vac on the gas tank and I found out the hard way on the freeway one day when the engine began to cut in and out-pulled over to disconnect the hose and vent to the atmosphere and then when I got home I cut about 2" off the metal pipe which was rusted and hooked everything back up-good to go now.

Mon Oct 09, 2006 1:45 pm

I have one of these setups (spare) if you're interested.

Mon Oct 09, 2006 2:22 pm

I don't think you have any worries about venting the tank if you remove the entire charcoal system. I have owned 4 things now and have tried new gas caps on all 4. All four will leak from the cap if there is more than 1/2 a tank of gas in the car and you take a few turns. The point is, if it is not water (gas) tight then it is definitely not air tight. That being said, I would connect the charcoal system if it was 100% intact. But I have never seen one that way yet..