Noob gas tank question

[bcOH67]

So I’ve been told my tank spits out gas by the filler tube on a hot day if it’s too full because it’s vented and this is normal. …is this normal?….

If this is normal, are there any upgrades /changes I can do to make it operate like a modern car that doesn’t do that? Been toying with the idea of switching out the carb for efi- would this do anything to change that?

I’m a noob…I know nothing…don’t beat me up if I sound dumb haha.

Thanks for any advice!
Brian

 

[dadsbee]

Adding what car would help.... but I'm assuming a 67 with a quarter panel filler.

Take a rag with you to the gas station... stick it in the filler, insert nozzle and then wrap the rag around the nozzle. That way the kick off pump system will work from back pressure as designed.

 

[bcOH67]

Sorry I’m used to just posting in the 66/67 charger forum. Yeah, 67 Charger with the quarter panel filler.

It works fine at the pump. I mean after I’ve filled it and park it in a parking lot- if it sits in the hot sun it builds up and spills out. But only when it’s full or close to it

 

[493 Mike]

Sorry I’m used to just posting in the 66/67 charger forum. Yeah, 67 Charger with the quarter panel filler.

It works fine at the pump. I mean after I’ve filled it and park it in a parking lot- if it sits in the hot sun it builds up and spills out. But only when it’s full or close to it

Gasoline does expand quite a bit when heated. It is coming out of a underground, cool tank into ambient temperatures so maybe fill less?
Mike

 

[Jerry Hall]

I don't think this is normal by any means. The vent system on a 67 vents any excess fuel right back into the tank, and any fumes just dissipate because the filler cap is vented. The only problem I ever encountered was a bad filler neck grommet that leaked when the tank was filled all the way. Turned out that the filler neck tube wasn't properly aligned with the tank because of a bent tab that secures the filler neck to the frame.

 

[Cojohnso1]

Is your filler cap vented? The next generation that goes to a fuel neck behind license is even in worse shape with this issue. Obviously can't use a vented cap if tank is over 1/2 full. And you accelerate? Fuel will leak from behind license plate. At least with '69. There is a trunk relief hose. But this typically can get less efficiency over time. And with today's gas that creates more fume pressure? It goes to the 2nd hose relief that spills on the rear-end. Thus on ground.

On a 66-67? Make sure you are using a functional vented cap.

 

[bcOH67]

From what I can tell, there are no leaks. No dampness or moisture of any kind around the filler neck or tank. Yes I have a vented cap but I don’t know how to tell for sure if it’s functioning correctly. Maybe I’ll just see if I can find a new one.

 

[threewood]

I have a full efi system including tank. If I fill the gas tank up and drive it home and park it it will puke fuel from the vent. So no, efi will not solve it. Just don't fill it all the way.

 

[bcOH67]

Oh good to know, thanks threewood.

 

[bcOH67]

OK, so I bought a new fuel cap that is vented, just to see if that was the issue. It definitely helped the smell a lot. But now when I take it off to fill it up, it lets out pressure when I take it off. The old one didn’t do that. Is this how it’s supposed to be?

 

[Davefinan]

OK, so I bought a new fuel cap that is vented, just to see if that was the issue. It definitely helped the smell a lot. But now when I take it off to fill it up, it lets out pressure when I take it off. The old one didn’t do that. Is this how it’s supposed to be?

I had a car that did that years ago also , so I’m interested in hearing some answers on this.

 

[Stonehengeheel]

My 67 Coronet does that as well. Always has I think. I have had it 20 years or so.

 

[mrmolding]

I recently noticed that my 70 RR is making a whooshing/pressure sound when I remove the gas cap. I am driving in 90+ weather so I understand that heat makes more pressure/vapor, but with two open vent lines does an almost full tank get so full that it blocks the vent lines to relieve pressure?
I know that 73 RRs had a pressure vacuum gas cap that is supposed to let air in and out as well. It is in the back like on my 70 RR. The 70 cap is non vented and the 73 is pressure vacuum, so I don't think these 73 caps let out fuel when going up and down hills -- or do they?

Just for fun I tried a pressure vacuum cap on my 70 and I still get the pressure release. Maybe I have an over full tank and a bad pressure vacuum cap? Both vent lines are clear since I blew air in them and felt the air out of the filler neck.