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Thu Feb 06, 2020 9:24 am

I'm having an issue with my '70 Beetle Sedan. After filling up the tank a few days ago I noticed a very strong gasoline odor.

I opened the trunk and found there was gasoline being forced out the top of the tank around the sending unit (see photograph).

Upon opening the gas cap, there was an audible rush of air and I could visibly see the tank decompress a bit.

Not sure what's going on here. I did replace the tank very recently but haven't had this problem the last few fills. Not sure how this is supposed to vent properly. It has always smelled like gas since I bought it last summer, but I've never had actual leaking before now.

There's a small hose running from a small outlet on the tank that runs to the filler neck. However, I don't understand how that's supposed to vent the tank because it's till before the gas cap and has no way to get out.

There's an old charcoal canister in the trunk that isn't connected to anything. From what I understand, that is used in part for venting, correct? Should I set that up again? If so, how should that be routed?

Oddly, the engine runs fine and doesn't seem to be having any issue with fuel starvation from vacuum in the tank. It only has an issue with positive pressure (so far).

I noticed the sending unit wasn't very tight either and tightened down the screws. However, after it sat overnight, I checked again this morning and there was some gas around the sending unit again, although it wasn't as bad as yesterday.

I just left the cap loose on there this morning before leaving so it doesn't leak all day.

Thanks in advance for any advice!

Thu Feb 06, 2020 10:01 am

That small hose runs from one side of the tank up and over towards the filler neck. There should be a T pipe like this: https://www.thesamba.com/vw/classifieds/detail.php?id=2174059

Those hoses then connect to the charcoal canister.

You will need to hook everything back up before the summer as this is how you keep your gas tank from collapsing.

Thu Feb 06, 2020 10:18 am

I'm not sure I understand how the T fits in here. The charcoal canister has two of those smaller hose fittings, then there's a small hose fitting on the tank as well as the neck.

Where do those two larger fittings of the T work into things?

Thu Feb 06, 2020 10:19 am

Take a picture of your gas tank area so I can see your setup.

Thu Feb 06, 2020 10:56 am

I know these aren't the best pictures. I can take more when I'm home. As you can see on the bottom left of the charcoal canister, there's a small port there. There's another port on the opposite end with the same size port.

That hose next to the main filler neck hose runs up and stops just after the gas cap. There's also another smaller fitting on the filler neck. That has a small hose that runs over to a small fitting on the driver's side top of the tank.

That hose is very very long as if it used to go farther, or a PO just didn't trim it down. When I replaced the tank, I just left it as is although I was planning to trim it down eventually. The canister was never connected to anything since I've owned it.

Let me know if you need more pictures of it and I'll try and throw some up on here later.

Thu Feb 06, 2020 11:04 am

Clogged vent will cause this. the evap can if so equiped can become clogged. For me an a vw van, it was clogged by a spider nest Now I prevent entry of spiders into that vent by making a wire screen thimble that fits in the vent tube.

Bug On! Never Under Pressure!

Thu Feb 06, 2020 11:15 am

That smaller secondary hose is where the T plugs into. The two big ends go on there. Just splice the T into it. Then a smaller diameter hose comes off the T and goes to the canister.

Do you have the small evap port on the far side of the gas tank as well? There is another hose that runs up and over the gas tank for it.

Thu Feb 06, 2020 11:38 am

You need to vent the tank properly, and replace the gas gauge gasket.

That is not the charcoal cannister in the truck. It is the expansion chamber. How it is originally routed is that small lines run from the tee vent and the vent on the tank to a tee near the windshield area of the truck then into the expansion chamber. Then a line exits the expansion chamber and is routed to the back rear tire area where the charcoal cannister is attached. The line from the fuel tank goes into the charcoal cannister and there are two hoses one from the top of the fan shroud and another from the air cleaner. The gas smell gets blown into the carb when running.

A lot of the lines and pieces rust over the year. You have to check all of your lines and metal pieces to make sure they are not rusted close and hold air tightly. You need to make sure your fuel lines are good too and the hoses and clamps do not leak.

You can search for fuel tank venting posts to see how older fuel tanks are vented. They would just run the vent line up high towards the windshield then back down and out of the truck to exit on the ground.

Whichever way you decide to go you need to make sure you vent your tank properly otherwise a suction will be created which will impede gas flow and will actually suck in the gas tank and collapse it. Lack of fuel = fuel starvation and cutting out, lean, and possible engine damage.