This week I finally put in a full tank of gas. I get home and into garage only to have heavy gas smell. I trace three hoses coming off my plastic expansion tank:
1. small> goes right back to tank
2. large> goes to below car, like an overflow (I plugged with white cap as in photo.)
3. small> goes back towards cab, and couldn't trace from above??
Then I notice the absence of charcoal cannister. (same postion on '76?)
smell stopped but..........
see photos:
Can anyone explain?


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Carb converted cars to smell of gas as today's fuels have a higher vapor pressure than the fuel that was available when carbs were the standard.

Hooking up a charcoal canister with the lines routed properly back to the engine will help somewhat, but you'll never get rid of the smell totally as long as you have carbs.

As one with two 914-6s running carbs, I know the smell all too well! It's enough to make me want to convert my conversion car to EFI.

In late 74 and later 914s, the charcoal cannister would be in the engine bay, usually hanging off of the battery tray. The small hose that disappears from the expansion tank would connect to a hard line through the center tunnel next to the fuel lines. That connects to a small hose that goes to the cannister.

The large line you plugged might indeed be an overflow. There is one that runs from the recess around the filler neck.

--DD

Your bottom picture is the overflow from the filler neck that is a thick hose that runs straight down under the fuel tank through the chassis to the ground.
As mentioned earlier your vapor smell is probably from the carbs.

My problem was the seal between the expansion tank and the top of the fuel tank, I changed the gasket and bought 8 new m5x16 bolts with lock washers and my smell went away. I have a 2.0 D-Jet so different animal.

Vysoc

I got to mitigate this smell before I get put out in the rain. I need my garage space . The car sat comfy in garage with only a 1/4 tank of gas for 3 yrs and did not smell of gas. Now that tank is mostly full (no way overflowing) it smells like I'm storing a boatload of molitov cocktails, .
Could there be a seam split in tank, just at a higher level so it only leaks when tank is full? (albeit no visible drips to be found, I had a large piece of cardboard beneath the tank to identify any drips).
Here's a photo of the larger diameter hose that was apparently used as an overflow, next to the petrified gas cap gasket.
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Here is the back of expansion tank where hose was connected to, and now covered with rubber cap I found that just coincidently fits tight.
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Fist off, get it out on the road and use up the gas, get it down to a 1/4 or less. Or drain it into gas cans. That will not only solve the smell issue in the garage (most likely), but will make the tank a lot lighter for when you lift it out to check for rust.

The felt/carpet pads under (and behind) the tank like to retain water, over the years they rub the paint off the tank, then when they get wet, they cause rust. Symptoms point to the rear pad, about halfway up the side of the tank.

It sounds like it's time to pull the tank and check for pinholes at those spots. Change out all the hoses while you're in there. One time I found a DAPO had put hose marked "Fuel Vapor" under there, it was all swelled up and about to burst... That time it was really dripping once I put any gas in it.

The gas tank sits on three felt pads, one on the front of the compartment and two on the back. They're about 1/3 of the way up, but the bottom of the tank is narrower than the top. These pads, if they ever get wet, tend to stay wet. This can lead to the ugly "R" word: Rust.

That is one possible source of a gas smell, a rust perforation in that part of the tank.

The top of the tank looks really nice; was the whole thing refinished?

--DD

Could also check the fuel hoses underneath your tank. Maybe they're slowly seeping, especially with a full tank.

Any help with ideas?
Trying to troubleshoot this thing from my damn damn wheelchair without the use of my limbs is a bitch. I used to be able to crawl under any car to fix it but now having to rely on others is a 'bee-och'.
All comments are appreciated.

Organise a teener work party and I'm sure you can get a couple guys out there to help you. Buy the most common parts that go bad so you are prepared when the guys come over. I'm a couple hours away but with enough advance notice I'll stop by. Mark

Mine had Webbers and no gas smell. Lucky I guess.