What vent hose do I need?

[Leonard Hooks]

My 70 KG has the gas tank vent hose in the front drivers side, with a hose running across the compartment to the metal tube that goes to the motor. But I have dual carbs so the vent tube just enters the engine compartment and is stubbed off. It is not connected to any thing. My hose has a T with a tube to go to the wheel well, but it is old and broken off.

My PO installed the carbs. Is there some way to connect the vent hose? Do I need the vent hose going to the engine compartment? If I'm not connected to the engine, do I need anything more than a way for air to return to the tank?

I'm also chasing a fuel smell when I do a hard left turn. So this may be related.
attached is a photo of the T area in the vent hose with just a broken short piece of tube.

_________________
Ghia again...after 48 years
1970 Karmann Ghia, Irish Green
1965 Mustang
Owned a 1971 Ghia, Irish Green from 71-77
Owned a 1982 Porsche 924

[Rob Combs]

I made my own charcoal canister to mitigate the fuel smell.

Cheap amazon aluminum can with a screw top. Punched holes for 6mm grease zerks with the check balls and springs drilled out. Threaded a nut on the back of the zerks to lock them in place. Filled the canister with fish tank charcoal. Plugged the fuel vapor hoses onto one end of the canister. Vented the opposite end to the atmosphere. Made an aluminum bracket to hold it all in place.

Fuel smell gone.

Matters not what your carburetor situation looks like.

[22manybugs]

If your lines are hooked up correctly, I can almost guarantee the fuel smell is coming from that short piece of hose not connected to anything.

Borrowing a sketch from sjtc, this is how the vapor lines should be connected:

(The sketch comes from this thread that has lots of good information):
https://www.thesamba.com/vw/forum/viewtopic.php?t=563405

The "T" connector on the right side in the trunk has three lines:
- One line (colored red in the sketch) goes high in front of the dash to the other side of the car and connects to the gas tank on the left side.
- One line (colored blue in the sketch) goes to the expansion tank on the right side of the trunk.
- One line (colored yellow in the sketch) follows the red line about halfway across the car, makes a U-turn, then connects to a pass-thru metal tube through the body. This continues with a line in the right fender down to a metal tube that runs to the back of the car.

Find out which line is missing, get new fuel line and reconnect. That line is small, the sketch says 3.5 mm (1/8"), I think I used the next size larger (5/32"? 3/16"?) and hose-clamped everything. You can get small fuel line from Amazon.

You said the line at the back is "stubbed off", does that mean it is open or blocked? If the line back at the engine is open to function as the vent, you likely should not have a problem with fuel smell. If it's blocked, it needs to be open assuming all the other lines are connected. Right now, the tank is venting through the missing hose at the "T". My car has the tube from the front to the back missing, the line ends at the bottom of the front fender behind the wheel, and I only have fuel smell when one of the vapor lines in the trunk is cracked/rotted. If you do still have gas smell after making sure all the vapor lines are connected and in good shape, then you can make a charcoal canister like Rob said.
_________________
Lon

1969 Karmann Ghia convertible
1971 Westfalia camper

[Leonard Hooks]

Thanks, Ron. Very helpful.
What I don't yet understand is why the hose running from the tank goes to a charcoal filter in the back...and the air filter...and the fan shroud? I assume to collect and burn off gases. But without something to pull it back there, how does that have any effect at all?

My vent line just stops. (I will check to make sure it is clear.) But I'm don't seem to have anywhere to connect it and I'm not sure of its importance. Since I have dual carbs, I'm way past making it original.
_________________
Ghia again...after 48 years
1970 Karmann Ghia, Irish Green
1965 Mustang
Owned a 1971 Ghia, Irish Green from 71-77
Owned a 1982 Porsche 924

[22manybugs]

The charcoal canister in the rear is supposed to absorb gas fumes. With all hoses connected properly and in good condition, the gas tank vents only through the charcoal canister, so that stops any gas fumes being released to the air. With the engine running, air is pushed out the fan shroud through the charcoal canister, then fumes are drawn into the air filter and through the carburetor to be burned. I have read comments here that the air blowing from the fan shroud through the charcoal canister helps purge fumes that are trapped in the charcoal, so the charcoal will last longer. In any event, if the charcoal canister has been trapping gas fumes for 50+ years, the charcoal in it probably isn't doing the job anymore.

There are posts here on TheSamba that describe cutting open the charcoal canister, replacing the activated charcoal that's inside, the re-sealing the canister. That's a good idea if the original vapor system is still all there and connected properly, but that doesn't apply for a lot of people that the original system is not there.

If the vapor system is in good condition under the trunk and vents to air in the back with no charcoal canister, I have not seen complaints about gas smell inside the car. Gas smell inside the car always seems to be caused by a broken/rotted vapor line up front. For myself, the vapor line ends at the lower right front fender where it is supposed to connect to a metal tube to the back, but the metal tube is missing, so it vents there at the lower fender. The couple times I have had a gas smell I find a problem with the vapor lines up front.

If you are sure all the vapor lines are in good condition and connected, the line vents to atmosphere in the back, and you still get a gas smell, then adding a charcoal canister at the exit point (like Rob describes) might help. A charcoal canister also is good for the environment by trapping fuel vapors. The activated charcoal could be replaced regularly using a metal can with a screw top. I plan to try making one from an aluminum water bottle with a screw top. Since I don't have the vent line running to the back, I plan to connect it to the yellow vent line just before the line exits out to the fender. I have the bottle, activated charcoal, and fittings to connect hoses, I just have not set aside time to work on it yet.
_________________
Lon

1969 Karmann Ghia convertible
1971 Westfalia camper

[David Bunin]

Bear in mind, the image was revised while that thread was being created. Here (I hope) is the final version with the corrected connections. The important difference is that the yellow line (the one that runs to the canister in the engine compartment in the back) comes off the high end of the expansion tank, not from the Tee fitting. I believe the idea/reason is so that liquid fuel only exists in the front-end plumbing, and that only fuel vapors leave this area for the engine bay.

[22manybugs]

Thank you for catching that, David. I grabbed the wrong sketch and probably created more confusion.

The recommendation is the same: Find where the cut line is supposed to go, get new fuel line and reconnect. But use the later sketch that David included above.
_________________
Lon

1969 Karmann Ghia convertible
1971 Westfalia camper

[22manybugs]

I also want to add: once you reconnect the missing vapor line and make sure all the other vapor lines are connected, if you still get gas smell, check the gas cap seal, the fuel sender unit seal, the main fill line (large diameter) and overflow fill line (intermediate diameter - about 5/8" ID - that runs parallel to the main fill line). If the fuel sender seal or either fill lines are leaking, gas will weep out when the tank is completely full and you can see the wet areas.
_________________
Lon

1969 Karmann Ghia convertible
1971 Westfalia camper