Fuel leak after gas added

[scottmercer]

Hello,

Mine is a 1978 Spider 124.

To reproduce issue I am having:

- Add gas to the tank, even just 1/4 tank.
- Drive 2 miles
- Park
- Within several minutes a fuel drip develops coming from the rear quarter panel driver's side
- No dampness noted within trunk near gas tank or any visible hoses

To fix:
- Remove gas cap
- Let sit for several minutes
- Leak stops.
- No leaking noted again until next time I get gas

What would the likely cause of this? Also, do I have to remove the rear quarter panel to investigate? If so, how is this done?

Thanks in advance!!

[TX82FIAT]

The 78 should have three tubes running from the tank into the area of the 1/4 panel referenced. There is a breather tub that connects back up to the fill hose and tubes that connect to lines that run through the back wall into the cabin. I looked real quick for a diagram to identify what line is what. You should be able to take the floor boards up in the trunk to expose the tanks and the routing of the lines in the 1/4 panel areas. finding a leak can be difficult. I'd use paper towels in suspect areas and if that does not work then consider some talk powder and clean up after done. The release of the cap makes me think vacuum?

[scottmercer]

I am thinking vacuum, too. Unfortunately, I think the leak is occurring underneath the trunk floorboard where the filler and hoses route behind the trunk's sheet metal. Looks like I might have to remove the quarterpanel.

[klweimer]

Perhaps the big rubber hose from the gas cap area down to the side of the fuel tank? You shouldn't have to remove the quarter panel to see everything. (at least not on the later '82 that I have) Instead of vacuum in the tank, it may be building pressure if the venting system has been goofed with. Does it make any noise when you take the gas cap off?
Kirk

[scottmercer]

Yes, it makes a hissing pressure release sound, not too much but definitely a sound.

[klweimer]

I would try driving the car with the gas cap off to see if it stops leaking. If so, you should probably go through all the vapor lines and connections to make sure they are correct, not collapsed and that the charcoal canister is correctly plumbed. A lot of PO's have jacked around with this system, under the impression that it was power robbing "emission control crap". If this system is working correctly, that's not the case. The diagrams for this system are in the factory service manual, and I'm pretty sure are here in the forum as well. That said, I would still look at replacing the fuel filler hose to the tank (and maybe all the others as well). It's a neglected part, as it is hard to see.
Kirk

[azruss]

Sounds like your big fuel filler hose is leaking under pressure. Replace it before it starts leaking all the time. AR sells new one.

[lglade]

If your fuel hoses are original to the car, then you're probably well advised just to replace them all and have it over with. My car had a constant gasoline smell (my wife hated my car for it). I searched for the culprit, but I was able to find several cracked hoses under the car and in the engine compartment, so I just made it my mission to replace them all. When I was finished (about a day in total effort), I had the confidence that my car was safer...and that fuel smell was finally gone too.

[scottmercer]

Thanks all - will replace everything.

[RRoller123]

If your fuel hoses are original to the car, then you're probably well advised just to replace them all and have it over with. My car had a constant gasoline smell (my wife hated my car for it). I searched for the culprit, but I was able to find several cracked hoses under the car and in the engine compartment, so I just made it my mission to replace them all. When I was finished (about a day in total effort), I had the confidence that my car was safer...and that fuel smell was finally gone too.

+1 on this, spent less time redoing every single line than the endless searching by nose for a tiny seepage. Smell is completely gone now, and all new lines means some confidence for quite a few more years!