Fuel tank leak

[Matt G]

Filled up my 70 a few days ago and as I walked by to pay, I noticed a bunch of my fuel leaking out all over my muffler. 
After a mini heart attack, I dove into the puddle of fuel to find the leak region.  Figured that it was high on the tank, so I ran into the shop to manage the risk and find some resolution tools, only to discover a really, really stupid attendant.  While imagining my car sparking into a ball of flames and blowing up Kellyville, I searched the store for a petrol can and a hose - thinking that I've only got to drain enough fuel to get below the leak.  No hose anywhere. She gave me a coffee cup... Stupid me, actually tried to scoop fuel out of my tank with the cup.  Didn't loose the cup, but it didn't work either.  Now fuel on the ground up my arm and over my trunk, and I was considering chopping up their air hose.....  Spark now. I dare you!
Back into the shop. Attendant says " if it's leaking too much I have to call the fire brigade". Now imagining my wife framing the newspaper article after car blows up, after fire and news crew arrives, etc, etc, etc.
I Ran back out to my car and the leaking has mostly stopped  .  Put down absorbent socks and pads, made a "please help" call to my darling ( value = 10x brownie points  ) and then had another look under to learn that I had a hose clamp missing from a fuel line.  Figured that it was too high to be a feed line, but wasn't sure, so with some tools delivered from home I drained about 20L out to make sure.
Just checked my build manual to learn that it's probably a vapour return line.

Questions:
1. Has this happened to anyone else?  Any tips?
2. Should this have a check valve or something to prevent flow out of the tank?  Or should I just simply treat it like a pressure line and clamp up everything?
3. I can get to the bottom of the hose, however I can't see the top of the hose due to my muffler.  Is there a secret to get access to it?
3. I've got a big ass carbi on my car. Why would I have a vapour return line?

Any feedback would be appreciated.

[rosco]

are you talking passenger side of a left hand drive or the drivers side as there are lines from both sides.

Rosco

[Scott]

Not knowing what a 70 is set up like, I'd guess the vapour line is more likely your tank vent line.  On older C3's, the tank vents through a vented gas cap, which can cause fuel smell and fumes.  Newer cars vent the tank via a hard line that runs up with the left hand side with the brake line to the front of the car into a charcoal canister.  The canister should vent to the air cleaner which sucks up any fuel vapour or fumes.  The fuel line to the carb should run up the right hand side.  My 73 has the hard vent line to the front, but no charcoal canister as yet.

[Matt G]

Lines ran down the passenger side - she's LHD.
I Managed to get my phone up there tonight and kept taking photos until I could see what was going on. 
There are two lines (steel tube line) running up along the passenger chassis. One is my fuel feed line and the other one is this one.  I think it's capped off in my engine bay (need to check that one in the morning).
Looks like I only need one clamp at the bottom. Strange that there's nothing the manage flow, but I guess that if all capped and tight, then there's no need for check valves, etc.  Going to be worried each time I brim out my fuel tank in the future

[wabco40]

Lines ran down the passenger side - she's LHD.
I Managed to get my phone up there tonight and kept taking photos until I could see what was going on. 
There are two lines (steel tube line) running up along the passenger chassis. One is my fuel feed line and the other one is this one.  I think it's capped off in my engine bay (need to check that one in the morning).
Looks like I only need one clamp at the bottom. Strange that there's nothing the manage flow, but I guess that if all capped and tight, then there's no need for check valves, etc.  Going to be worried each time I brim out my fuel tank in the future

The 3/8" line on the right side is the fuel feed and the 1/4" line beside it is the fuel return. The original fuel pump had a return outlet fitted to it. Newer or aftermarket pumps do not have this. If the 1/4" line is only capped in the engine bay then you would be better off capping it off at the tank. Sounds like 1/4" rubber hose that goes from the tank to the hard line may be perished.

[72vet]

  It's one of these two hoses which have perished.

[bfit]

Now there is a helpful photo
Bfit

[wabco40]

It's one of these two hoses which have perished.

Good picture but other side. That's the vapour side.

[72vet]

You guys are never happy. 

[wabco40]

You guys are never happy. 

Now that's a picture 

[bfit]

Now that's a picture 

I thought that one was the return line.
when I fill mine to the bottom of the neck, fuel will come  out the cap under acceleration
So I don't fill it rite up.

another reason for not filling rite up is
if you park nose down on a slope fuel can siphon to the engine.
we have seen that happen.
Bfit

[Matt G]

Thanks guys. Yep definitely the second photo...
I didn't quite have the time or the space to lift th body off, so I cleaned up the tube with some scotchbrite and added a clamp using my smallest hands, and my tongue carefully placed to the side.
My vapour line is capped in my engine bay.  In what situations would I need a vapour line??  Air in my lines that is squeezed out by my fuel pump?? :huh:I
Isn't your fuel system a closed, but one way fluid system? Just curious. I might want to connect it up again one day, so if it's possibly going to get used, I'll keep the front cap to keep the tube clean.  Otherwise I'll loose the whole tube and cap the rear.

Cheers