Pressure in new tank- found out why

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Fittrjoe

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So I had a new gas Tank and sending unit installed on my 67 Barracuda about a week ago by a trusted dude that I use a lot.
Anyway I went to fill up today and noticed pressure when I released the cap.
Upon investigating, I found a Port on the new Sending Unit cover plate that is NOW tied into my filler tube vent with a new rubber hose. Before I ask my guy why, I wanted to check with ya'll and ask ... Is this normal? I mean there IS a port there. I know for a fact the old tank does not have this and vent WAS open to atmosphere.
BTW Its a 360LA crate motor and is running fantastic since new tank ( 150 miles)
Just concerned about pressure and new set up. Trying to learn.
Thanks
 
67 A bodies have a tube on the top of the filler neck that goes to a U shaped hard line tube that follows the filler neck down through the trunk floor and terminates open to the atmosphere inside the rear driver's side frame rail.

The extra tube on the sender is for later years return line from the fuel filter with 3 tubes.

The mechanic tied the return inlet to the vent on the filler neck thereby eliminating the tank vent.

Without a tank vent 2 things will happen..


The tank can collapse from the suction of the fuel pump. ( I know it's not the suction it's the weight of the atmosphere pressing on the outside and with a lower pressure inside, the tank collapses)

And...

As the fuel expands as the temperature increase and the tank without a vent builds pressure.

Stock 67 filler tube.


Screenshot_20240317-184219~2.png


Stock 67 sender (the sender internal shape is unimportant for this conversation)
Screenshot_20240317-184512~2.png


Later model sender with return

Screenshot_20240317-184641.png



Have the mechanic properly cap off the return (it will be submerged in fuel when the tank is full)

And reattach the proper tank vent.
 
Last edited:
Dana67Dart said:
67 A bodies have a tube on the top of the filler neck that goes to a U shaped hard line tube that follows the filler neck down through the trunk floor and terminates open to the atmosphere inside the rear driver's side frame rail.

The extra tube on the sender is for later years return line from the fuel filter with 3 tubes.

The mechanic tied the return inlet to the vent on the filler neck thereby eliminating the tank vent.

Without a tank vent 2 things will happen..


The tank can collapse from the suction of the fuel pump. ( I know it's not the suction it's the weight of the atmosphere pressing on the outside and with a lower pressure inside, the tank collapses)

And...

As the fuel expands as the temperature increase and the tank without a vent builds pressure.

Stock 67 filler tube.


View attachment 1716223064

Stock 67 sender (the sender internal shape is unimportant for this conversation)
View attachment 1716223067

Later model sender with return

View attachment 1716223068


Have the mechanic properly cap off the return (it will be submerged in fuel when the tank is full)

And reattach the proper tank vent.
Click to expand...
Everything you said is what I expected.
I will rectify this ASAP.
THANKS SO MUCH !
 
Yeah well, that may be true in this instance,
But, the vapor canister is about as maintenance free as it gets, it keeps my garage from stinking, keeps my 87E10 from going stale in the tank right away, the vapors may contribute to mpgs, and, I always have at least one or two kicking around anyway.
 
I just had to replace the canister on my 96 jeep GC. I had to remove the front bumper cover to access it.

I'm a bit jaded :lol:
 
On my 62 i didn't see a vent on the sender or fill neck? were the older cars more different? vented cap?
 
Icetech said:
On my 62 i didn't see a vent on the sender or fill neck? were the older cars more different? vented cap?
Click to expand...
There is a vent somewhere.

Edit: Well I was way wrong!:(

What I was remembering as a vent was the fuel pickup tube which is separate from the sender in my 56 pickup

The cap would be the only choice.
 
Last edited:
Dana67Dart said:
There is a vent somewhere. A 56 Ford Pickup I had had a vent tube from the top of the IN CAB tank to out the bottom of the cab floor. An external tanks I have had, had a vent more like a differential.
Click to expand...

hmm.. k... well i might have an issue :)
 
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