Gas shooting out of my filler tube

[67 GTX]

Lately on my 67 gtx, I've had a strong fuel smell in my garage. Upon inspecting further and opening the gas cap, fuel will gush out for a few seconds. This seems to happen when there is a temperature change, or if I have jacked up the front of the car for work (and then lowered it back down).

The tank is new, and I blew out all the vent lines when I replaced it.
I do have a reproduction gas cap on the car if that matters. Perhaps it's spring is too tight and it's not letting vapors vent? But this is a more recent issue, and the cap has been on for years.

Has anyone experienced this issue or have any ideas as to what is going on?

 

[oldbee]

Sure sounds like a plugged vent.

 

[Bill Monk]

OLDBEE is right, sound like a tank vent problem

 

[Fran Blacker]

I assume you have a flip open gas cap. Can you put a standard vented cap on to experiment if that stops the problem?

 

[PurpleBeeper]

I was thinking vent too......BUT, after I thought about it I changed my mind....then back again.

a) Is this car fuel injected with a return line? If the vent was blocked, it could build up pressure.
b) Carburetor/no return line? Yeah, if the vent was blocked & the tank was "sucking in", when you released the vacuum (open the cap) the gas could slosh around and come out when the tank snapped back into shape.
c) Is the tank just very full...maybe a little too full? (e.g. your favorite gas station has the car pointed down hill) I'm not to familiar with the 67's, but if the filler is down low that could happen. I don't think this is possible if you have a flip-open fill cap up on the fender (it's uphill to the cap)

 

[1969CoronetR/T]

I had the same problem for five years or more. The local shop cleared all the vent lines and I installed a new non-vented cap to no avail. Bought a new stainless steel tank and the problem went away. My old tank, for some reason unknown, was bulimic. Trouble free for the last few years with the new tank.

 

[67 GTX]

I can't install a different cap. The car does have the flip open gas cap.
It is a carb/no return line.

The filler points into the car, then takes a 90 degree turn and then points straight down, then turns again to enter into the bottom of the tank on the side. 67's have a very weird filler tube.

I believe there are 2 vent lines exiting the tank that vent into the filler tube. I'll inspect them, but I find it hard to think that the metal tubes compressed, since they're decent size. I can check to see if the rubber lines that connect to them have collapsed though.

I thought the issue was the tank was a bit too full, but I have ran the engine for a while and it still occurs.

 

[oldbee]

Yellow jackets,spiders love to build nests anywhere they can!!!!

 

[Ranger16]

Don't forget the mud daubers.

 

[Mopars & Missiles]

I believe there are 2 vent lines exiting the tank that vent into the filler tube.

If this is true, this would NOT vent your tank. The vent MUST be to atmosphere.

 

[Fran Blacker]

Here is a picture of fuel neck and tank, 1966. I'd maybe remove filler neck etc if you can't get at it in the car to clean vent tubes.

 

[67 GTX]

If this is true, this would NOT vent your tank. The vent MUST be to atmosphere.

I'll have to inspect when I get home later. The pic that Fran Blacker posted looks like my setup, which, I believe, it shows all vents going into the filler tube. I believed the vent was the cap, since it's gasket is spring loaded, and I assume opens under x amount of pressure.

 

[Bill Monk]

I'll have to inspect when I get home later. The pic that Fran Blacker posted looks like my setup, which, I believe, it shows all vents going into the filler tube. I believed the vent was the cap, since it's gasket is spring loaded, and I assume opens under x amount of pressure.

I don't think that cap is vented which is why you have the atmospheric vent (see Fran's post)

 

[Mopars & Missiles]

I'll have to inspect when I get home later. The pic that Fran Blacker posted looks like my setup, which, I believe, it shows all vents going into the filler tube. I believed the vent was the cap, since it's gasket is spring loaded, and I assume opens under x amount of pressure.

Well, I'm not familiar with '67's system. I have '69's and '70's where the cap is NOT vented, the vent is on the tank or filler tube. So somehow your tank has to be vented to atmosphere or pressure will build up from temperature change. Maybe on your '67 the cap IS vented??

 

[Fran Blacker]

On the right of tiller neck near gasket it says vent to atmosphere. Wonder whether you could look up under car to see if there is a vent tube opening ? Been a while since I looked at mine.

 

[ckessel]

I've been seeing more of this venting/pressure buildup going on since the fuels contain more alcohol and have a much lower boiling point now. Possibly the venting systems of old can't keep up with the amount being generated now? I know on my 65, after driving it for like 30 minutes or more I could here the fuel boiling in the tank after I shut it off. The TTI 3" pipes that were 1-2" away from it probably contributed to it but thats still not good.

 

[Fran Blacker]

See if vent is clear. This is vent to atmosphere . This picture isn't 66/67 the layout is close I believe. The ebay gasket on the left side you'll see a knockout for vent tube. not myion.

https://www.ebay.com/itm/Mopar-65-6...855358?hash=item4af3cca67e:g:HfAAAOSwjZJZ6lZ4

 

[67 GTX]

You are correct, I do indeed have a vent to atmosphere, as shown in the right most pic right above this post.

I put a rag into the filler tube to catch anything that might blow out, and shot air in from the tube that exits under the car. I didn't see anything come out, but I did confirm that at least now that vent is clear. So the issue should hopefully not happen again. If it does, at least I ruled this out.

I did inspect the metal pipes and rubber hoses that route the fuel back there, and none were collapsed.

 

[67Charger]

I'll share a little story... My '67 Charger has had MAJOR tank issues. The Charger does (did) not have the vent to atmosphere tube, nor a vent ANYWHERE except the cap that only allows air in.

1st problem was a filler vent issue. My thru-frame upper tank fill vent was rusted, so I ran hose under the frame rail to replace it. This ultimately caused incomplete fills and a P-trap effect allowing a column of fuel to build up in the vent tube. I had to get the right pipe so it flows flat or up at all times to allow the air past whatever liquid sloshes up there.

Second, the cap only allowed air in, not out. I had noticed a subtle bulge in the tank during the summer, and paid it no mind. Last month during a road race, the car shut off 2.7 miles form the finish. The tank had swelled nearly 5 inches. The pressure build up was immense and quite surprising when the cap was removed. Granted, a piece of road debris had knocked off a tail pipe at the muffler and pointed the exhaust at the tank, causing that severe boiling, but regardless, pressure could not get out. I have since taken the cap to a belt sander and sanded off the nub inside that holds the check valve so it breathes 2 ways.

 

[Fran Blacker]

Is the problem solved ?