Tank vent line is puking fuel

[Hilljack68]

Thanks Steve. My only concern with the vented is spillage on acceleration.. as my fill neck is behind the license plate. Seems like a potential for bleed-through.

 

[steve340]

Same as mine I have a 1968 GTX. No problem at all with with the cap under any conditions.
It can get fairly hot here in summer and the modern fuels expand like crazy.
It was a few years ago but I think the recommended cap was a 1973-75 B Body cap - but not super sure on that.
It was about 50 USD on EBAY.

 

[Hilljack68]

Sweet. Thanks much Steve! I'll give it a go.

 

[steve340]

It should work or at least help.
If you want me to post a couple of pics of what I did to the vents I can.
You do not need to modify the car or the tank it is only rubber tubes and grommets.
I believe I modified the vents first which resolved 95% of the problems - it stopped puking liquid fuel on the ground and the stink of raw fuel was largely eliminated.
I was paranoid someone would throw a cigarette butt under the car and set the puddle of fuel it had pushed out alight and torch my car.
However there was still a slight "whoosh" noise when I removed the gas cap. Air pressure was either going in or coming out - I think it was going in. A mechanical fuel pump if there is no air able to go in to the petrol tank it will pull a vacuum in the tank and the engine can starve or you can collapse the fuel tank.
When I fitted the later model fuel cap it was 100% sorted.

 

[moparedtn]

I run a vented cap on my '68 GTX - parts guy and I went through the Stant book one day looking for a suitable
one that would work AND he had in stock. In my case, it wound up being for a '73 Ford station wagon.

Ok, go ahead and tell me I shouldn't run a vented cap, experts....

 

[Hilljack68]

It should work or at least help.
If you want me to post a couple of pics of what I did to the vents I can.
You do not need to modify the car or the tank it is only rubber tubes and grommets.
I believe I modified the vents first which resolved 95% of the problems - it stopped puking liquid fuel on the ground and the stink of raw fuel was largely eliminated.
I was paranoid someone would throw a cigarette butt under the car and set the puddle of fuel it had pushed out alight and torch my car.
However there was still a slight "whoosh" noise when I removed the gas cap. Air pressure was either going in or coming out - I think it was going in. A mechanical fuel pump if there is no air able to go in to the petrol tank it will pull a vacuum in the tank and the engine can starve or you can collapse the fuel tank.
When I fitted the later model fuel cap it was 100% sorted.

Yeah, I'd be interested in seeing those mods.

 

[steve340]

The quality of the pics is a bit poor but I think you will be OK.
The first thing I did was use clear plastic tube and brought the vents up in to the trunk so I could see what was happening.
I did some experiments and found that on my car at least the fuel could push up either vent tube right up to the parcel tray height and then drop out the chassis rail.
I figured out I needed to change the pressure in the vent tubes so all I did was use adapter fittings to change from the 1/4 inch vent tube size to 1/2 tube. This change in size allows the pressure in the tube to change and the tube becomes a syphon breaker.
I went from both vents up in to the car, adapted to the 1/2 inch tube, went up to the parcel tray and then down to the chassis rails on both sides in large loops. Some tubing and changing a few rubber grommets and it was done. Most of it is hidden by the spare wheel and you do not really notice the black tubes up to the parcel tray.

 

[moparedtn]

The quality of the pics is a bit poor but I think you will be OK.
The first thing I did was use clear plastic tube and brought the vents up in to the trunk so I could see what was happening.
I did some experiments and found that on my car at least the fuel could push up either vent tube right up to the parcel tray height and then drop out the chassis rail.
I figured out I needed to change the pressure in the vent tubes so all I did was use adapter fittings to change from the 1/4 inch vent tube size to 1/2 tube. This change in size allows the pressure in the tube to change and the tube becomes a syphon breaker.
I went from both vents up in to the car, adapted to the 1/2 inch tube, went up to the parcel tray and then down to the chassis rails on both sides in large loops. Some tubing and changing a few rubber grommets and it was done. Most of it is hidden by the spare wheel and you do not really notice the black tubes up to the parcel tray.

View attachment 1472123

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Holy crap!

 

[Hilljack68]

I have the same tank and vent line set up on my 69 sport satellite. I have an aftermarket tank and factory vent lines that are all in good shape and hooked up correctly. My car will puke a little fuel from the vent line each time after I stop. When I stop the car and turn it off, it takes about two minutes for pressure to build and then it spurts a little gas out the vent line. I stop this by waiting the two minutes, then opening the filler cap and releasing the pressure. I can’t figure out why it does this, but it seems like it’s a common problem, even with everything correctly installed.

I had her out last night for a bit, and employed the same strategy. I shut down the engine, popped the cap off, it de-pressurized... and no puking. I still need to source a vented cap, but this'll work in the interim. Thanks.