Fuel tank seals and/or hoses are leaking

[Beach_Dude]

It's been a problem I've had for a long time. I even redid them since I failed the vacuum test during smog. So, I dropped the tank, new seals, hoses, the works.

However, a few weeks back I noticed gas dripping after a fill-up and always accompanied with a strong gas smell.

I know some shops have a 'smoke' machine to detect leaks... Does anyone know how this is done or how to get my hands on this equipment?

[wylder]

Get yourself a Kohler Multi use transfer pump part # RA990 from Amazon for $10 bucks a box of swisher sweet cigars and make your own. Put the cigar in the pump and attach the hose to your charcoal canister, pump away and trace any smoke to your vacuum or gasket leaks. I did this a few months ago when my Jeep failed smog for a vacuum leak. Traced it to the tank rollover seal. Saved the cost of a smoke test which was $100 and used the savings to buy the parts to repair my fuel tank. Hope this helps.
Wylder

[ShagWagon]

Did you change the filler hoses between the tank and fill cap?

If not pour some gas in there and look under to see if it’s leaking. I always try to use a dry paper towel to find fuel leaks and to make sure I got it fixed.

Hope it helps.

[Beach_Dude]

Ordered a evap smoke tester from amazon for like $129... The way I see it, I'm going to use it again at some point on one of my other cars and it pays for itself on the first time usage.

I'll keep you guys posted on how it works.

[Beach_Dude]

So the evap smoke machine was a massive fail... Not a single sign of smoke. However, fill up the car, park on an incline and fuel just spits out the back of the tank.

Ends up being the hoses at the rear of the tank, which I am pissed about because they're not only brand new, but if I tight down the hose. Clamps any more, I'm gonna crush the tank nipples.

Video of the leak: https://photos.app.goo.gl/6gaCkU8mvhFKcsCu7

Just gonna order some softer and thicker walled hose. Does any know the hose diameter for the 1978-1979 filler and vent hose diameter?

[SJTD]

I wonders if you have a crack. In the tank, one of the nipples, or a solder joint.

[Driftwood]

I replaced all my fuel lines in my 79. The fuel fill line is 1". The vent line is 3/4". Below is a list of all the fuel lines I replaced on my 79. The 1" was difficult to source.

Lets hope your vent line nipple is not cracked. I sealed my fuel tank leak with J-B Weld SteelStik. Over 2 years later the patch (upper right corner of the tank pictured below) still doing its job. No leaks!

1"
3/4"
5/16"
1/4"
3/16"

[rang-a-stang]

When I bought mine, the fill hose was already clear reinforced vinyl bulk tubing. I have never replaced it because it works. This stuff.


I am pretty sure it's 1" and 3/4" like Driftwood said.

Also, know there are 2 other nipples in that cluster. The one that goes up into the wheel well and eventually to the roll over check valve to the carbon can, and another nipple that goes to the vent on the top of the metal fill kneck. You can see both of those nipples in Driftwoods picture. The one with the paper towel stuffed in it goes up into your wheel well and the little small nipple is the one that should go back, aft of the axle, onto one of the nipples by the fill tube. Do you have all 4 of those nipples on your tank? Maybe one has cracked?