1967 Plymouth Barracuda - Fuel tank not vented properly??????

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soonercruiser

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Will the little problems PLEEEEEASE stop mounting up????? :rolleyes:

I was about to comment that it hadn't gotten all that hot yet in Oklahoma....BUT......
TODAY IT HIT 100 degrees F!
I went out into the garage after dinner, greeted by the strong smell of gasoline!
First thought was my new Barracuda project.
Sure enough! I've got gas dripping down from the fuel tank onto the floor.
(Thank GOD I had the garage door open; as we have a gas water heater in the garage.)

After immedaitely throwing one of my old large bath towels under the car, my memory kicks in, that someone months ago mentioned my fuel tank may not be vented properly.
So, I pop the fuel cap and am greeted by a quick slosh of gas on my hands.
Yes, the last time I drove the Cuda I filled the tank up.

With all the other stuff I have been fixing, I will plead ignorance or overwhelmed.
There is a vent tube running along the filler tube to the tank, that is connected up near the fender to the filler tube. Picture...

fuel tank vent tube 1.jpg


But, where the end runs down to the trunk floor that vent tube is merely poked trough a small opening in the trunk floor.
(So, I am assuming that the extra gas pressure from the tank seal at 100 degrees went down that tube, dripping on top of the fuel tank.
Therefeore what I saw "leaking" was probably dripping on top of the tank from that tube, and running over the side of it.
Picture to tube down end...

fuel tank vent tube 2.jpg


I will vertainly check out the Service Manual.
But, I figure someone can expalin the correct venting to me better tha poor diagrams in the service manual.
 
I don't know how that line is supposed to be secured on a fish, but that is EXACTLY how it is configured, with a "U" up high near the top of the fender.

And ending down into the frame rail is EXACTLY how it ends

If it is dripping fuel, it is VERY simple---your tank is too full. The fuel is clear up into the filler tube, clear up there at the vent line connection in the filler tube. Expansion will force the fuel up and over, and it will drain, until it gets below that point. In other words, "anti siphon" or "siphon breaker."

Your only correct solution is to not fill it that full.

Is it possible that your tank is damaged/ crushed and not as large as it should be?
 
67Dart273 said:
I don't know how that line is supposed to be secured on a fish, but that is EXACTLY how it is configured, with a "U" up high near the top of the fender.

And ending down into the frame rail is EXACTLY how it ends

If it is dripping fuel, it is VERY simple---your tank is too full. The fuel is clear up into the filler tube, clear up there at the vent line connection in the filler tube. Expansion will force the fuel up and over, and it will drain, until it gets below that point. In other words, "anti siphon" or "siphon breaker."

Your only correct solution is to not fill it that full.

Is it possible that your tank is damaged/ crushed and not as large as it should be?
Click to expand...
Was a new tank.
But you are correct in that I always try to "completely" fill my tanks when I gas up.
This is the first time I've EVER had this issue with any of my cars.

The applicable service manuel is not Barracuda specific. It's an A-Body manual.
That has consequences, in that start at p14-68 there are several diagrams with the vent tube that conflict on where it drains to.
One shows the overflow tube just exiting below the trunk floor.
Another has that tube re-entering the fuel tank.
(But that diagram has the filler tube on the opposite side from the vent tube....so maybe it is n/a for my model.)
And. they do not specify which is for the Barracuda.
So, I guess that I will just have to get under there and look at the tank.

But, simply venting out under the car doesn't make good sense.
But life itself was simpler back then.
 
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I have the same problem with my 75 dart but it doesn't have the line running back. So my pukes out the filler hole. Iv got to get it fixed before I paint it. I thought I had it straighten out with the new tank and return lines but the last time I filled up the next day I could smell gas and right under the fill cap was wet.
 
1) don’t fill up so full. No brainer
2) fuel today is not the same as fuel from when that system was designed.
You need to adapt. Like we all have.
3) gas hot water heater in a garage- make sure it is about 18-24” off the ground. How is that even code with fuel vapors hanging out at ground level.
You are very lucky! In New England we have basements for that stuff not garages. Even garages attached to houses are dangerous but legal. I’m lucky- our two car is a separate building. Only electricity in ours. Good thing your door was/ is open.
 
I checked the 67 supplement and nothing specific to cudas regarding venting. Here's pics from 69 manual(same in regards to 67)

20240615_092253.jpg


20240615_092306.jpg
 
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Syleng1 said:
1) don’t fill up so full. No brainer
2) fuel today is not the same as fuel from when that system was designed.
You need to adapt. Like we all have.
3) gas hot water heater in a garage- make sure it is about 18-24” off the ground. How is that even code with fuel vapors hanging out at ground level.
You are very lucky! In New England we have basements for that stuff not garages. Even garages attached to houses are dangerous but legal. I’m lucky- our two car is a separate building. Only electricity in ours. Good thing your door was/ is open.
Click to expand...
Yup!
That's standard plumbing code here too - up with the tank.
 
4spdragtop said:
I checker 67 supplement and nothing specific to cudas regarding venting. Here's pics from 69 manual(same in regards to 67)

View attachment 1716262689

View attachment 1716262690
Click to expand...
Yup! Thx.
Before I saw your post, I cleaned up the vent tube, replaced the rubber hose connector to the fill tube, and rerouted it as in your figure 2.
On my 67, there is a large rectangular gasket at where the filler tube goes through the trunk floor.
Towards the center line in that gasket there was a hole with a rubber plug.
I probed that hole with a small steel wire, and I believe that ic came out on top of the fuel tank.
But with really good lighting and a small mechanic's mirror, I could not confirm that.
So, I ran the vent tube alongside the filler tube, through that large rectangular seal/gasket, and made sure it went down alongside the tank - away from the exhaust pipe.
I really couldn't see any holes in the side of the frame rail.

Will retrain myself to not overfill the fuel tank on the Cuda! :rolleyes:
Thanks all....
 
Dartfreak75 said:
I have the same problem with my 75 dart but it doesn't have the line running back. So my pukes out the filler hole. Iv got to get it fixed before I paint it. I thought I had it straighten out with the new tank and return lines but the last time I filled up the next day I could smell gas and right under the fill cap was wet.
Click to expand...
Would be an easy fix.
When the tank is near empty, and with the filler cap/door open a while, you just have to "tap" a small fitting into the top of the filler tube to accommodate a short rubber hose connector and a small fuel-type line that you run to where you want the gas to vent to.
 
soonercruiser said:
Would be an easy fix.
When the tank is near empty, and with the filler cap/door open a while, you just have to "tap" a small fitting into the top of the filler tube to accommodate a short rubber hose connector and a small fuel-type line that you run to where you want the gas to vent to.
Click to expand...
Im assuming the end of the rubber hose would need some sort of check valve?
 
Bodyperson said:
The factory didn't give us a check valve. Mine was plugged with mud from Daubers.
Click to expand...
I don't remember ever seeing anything on mine from the factory. I'm assuming the later years the vent was part of the evap charcoal system. But mine had never worked since I owned the car it's always puked gas out of the filler
 
Dartfreak75 said:
I don't remember ever seeing anything on mine from the factory. I'm assuming the later years the vent was part of the evap charcoal system. But mine had never worked since I owned the car it's always puked gas out of the filler
Click to expand...
The old flip tops were never known for their sealing abilities.
 
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Dartfreak75 said:
Im assuming the end of the rubber hose would need some sort of check valve?
Click to expand...

Bodyperson said:
The factory didn't give us a check valve. Mine was plugged with mud from Daubers.
Click to expand...
Mine didn't have any check valve either.
And there was a pretty significant restriction at the top of the vent tube rubber connector up high on the filler tube.
So, I opened that up a bit, as I assume that would still pass gas just fine - just like I do! :)

That short rubber hose connector up top was pretty deteriorated. But, not plugged.
 
no check valve.

You seem to have a vent system that is older than your car. up through 1970 the vent was simple and ended inside the rear frame rail. it is actually design not to vent anything out of the tank, but rather let air into the tank to balance the fuel being pumped out. 1970 CA cars and cars after that have a complex system of tubes that route the vented vapor to charcoal canisters and such. Does your tank have 4 vent tubes that have been plugged (driver's side toward the top of the tank) or do you have a 70 and earlier tank (no vent tubes on the tank)? The other odd thing is that pressure built up in the tank so that when you opened the cap it expelled gas. If your vent tube was functional all the overflow would have come out the vent tube into the frame rail. it has to be plugged somewhere...

1971 and up tanks have a separate "tank within a tank". It can only be accessed with the fuel tank removed. If you have a later tank and the system is not functioning properly, that inner tank (part of the emissions system) could be leaking from the rubber plug on the top of the tank. You can only get to that plug by removing the tank from the car.
 
str12-340 said:
no check valve.

You seem to have a vent system that is older than your car. up through 1970 the vent was simple and ended inside the rear frame rail. it is actually design not to vent anything out of the tank, but rather let air into the tank to balance the fuel being pumped out. 1970 CA cars and cars after that have a complex system of tubes that route the vented vapor to charcoal canisters and such. Does your tank have 4 vent tubes that have been plugged (driver's side toward the top of the tank) or do you have a 70 and earlier tank (no vent tubes on the tank)? The other odd thing is that pressure built up in the tank so that when you opened the cap it expelled gas. If your vent tube was functional all the overflow would have come out the vent tube into the frame rail. it has to be plugged somewhere...

1971 and up tanks have a separate "tank within a tank". It can only be accessed with the fuel tank removed. If you have a later tank and the system is not functioning properly, that inner tank (part of the emissions system) could be leaking from the rubber plug on the top of the tank. You can only get to that plug by removing the tank from the car.
Click to expand...
I've got none of that later model features you mention in my 67.
It was really hot yesterday, probably compared to when I filled up.
And, I did notice the vent tube restriction and bad rubber connection when I worked on it today.
That's why I fixed those things.

I will also keep the gas cap popped when she's in the garage.
I trust the wifie not to steal my gas. :rolleyes:
 
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soonercruiser said:
Will retrain myself to not overfill the fuel tank on the Cuda!
Click to expand...
Pretty much all cars. Worst is winter fuel on a hot day. Look up "winter fuel RVP". Although what we're seeing when liquid fuel forces out is probably not the RVP directly, but regardless it expands.

str12-340 said:
no check valve.

You seem to have a vent system that is older than your car. up through 1970 the vent was simple and ended inside the rear frame rail. it is actually design not to vent anything out of the tank, but rather let air into the tank to balance the fuel being pumped out.
Click to expand...
^^This^^

The vent line goes back into the fuel fill. The flip cap itself should allow some air into the tank. Not so on later models which vent through intermediate devices - 1975 is probably a charcoal filter.

Later cars also seal up the air cleaner snorkel when the engine is shut off and vent the carb bowl to the charcoal canister when the engine is off. That might after '75.
 
I have a 67.
The vent tube runs into the framerail.
It's purpose is to let air in as gas is consumed, (and let air out as gas is pumped into the tank, if you ram the pump into the tube and and eventually pull back a little when you're tired of it shutting off automatically).

After filling the tank, the fuel would not and could not be higher than the bottom of the filler neck.

With the vent at the top of the filler neck, and routed higher, a hot day, a full tank, and fuel sloshing around, that could cause enough pressure to force fuel out?

When parked, eventually air would pass through the vent and eliminate the pressure, no?

If pressurized, wouldn't that mean the vent is clogged?

If pressurized wouldn't it be more likely to force fuel out of the fill tube/tank o-ring that is submerged in fuel?

If the vent was originally, correctly, run into the frame rail, and fuel was forced out of it, the framerail would be saturated in fuel, no?

Just thinking this through as something seems off here.

I've had a gas leak, different scenario, at the o-ring only when the tank was filled and the car sat for an extended period of time.
 
I'd be movin a water heater fo sho and fo certain.
 
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