Vented Gas cap for 69 ?

[Steverino]

I think I'm going to try a vented cap

I know there have been threads on this

After being apart for much work, put 15 gal in last night, and had a small "drip" from the vent in the front of the tank (short hose, connected to long internal tube per manual)

Not overly warm here (70 ish), and tank was only slightly over 3/4 full

I had the same issue before disassembling the car, long and short vent lines were blown clear with air, tank has been replaced (spectra premium ?) and the vent lines inside are actually incorrectly routed (per others photos and experience)

I made sure short vent hose connects to long internal tank vent tube, and that long vent tube into trunk is connected to short internal tank tube

Fuel lines were also changed (I don't think it has an effect, this only occurs on "cool down")
from 5/16" orig no return, to 3/8" with 1/4" return


Anyway, in the past, loosening the cap a notch alleviated the vent tube drips, so I'd like to try a vented cap without drilling this one if possible, but if someone has modified their non vented cap to work as a solution, I'll give that a go !

Thanks

 

[69sunfireGTX]

I'm sure you will have more leaks from the vented part do to the sloshing of fuel on stop and go applications. This is the way you have it?

 

[Steverino]

I have had the vent hoses connected both ways on the previous tank (which had the same issue), and had the same result

And actually the leak is a steady stream (or more steady drip) if the outside short vent tube gets connected to the short internal vent tube !

I'm not certain which way they are oriented currently (I can look again tonight), but I do know that I have the short external vent tube connected to the longer internal tube that reaches to the rear of the tank and the longer vent tube into the trunk connected to the shorter internal tank vent (near the front of the inside of the tank)

This is because I am pretty sure the current aftermarket tanks do not always have the original vent tube orientation, although they do have the long and short internal vet tubes, pinched at the ends slightly inside the tank

I'm not sure the vented cap will work, but don't want to modify the existing cap unless I'm sure it won't create more of a leak !

 

[Bill Monk]

Something isn't right. I just installed a new tank and have no issues, you are correct in that the long internal tube connects to the short vent line that attaches by the shock tower and the short internal tube connects to the long vent line going into the trunk. If the vent lines are open, you should not be having this problem. If you are sure they are connected right, try blowing air through them

 

[Steverino]

In thinking that the issue is/was in the trunk vent tube, I actually removed it and snaked welding wire through it (in addition to blowing air through) to be certain it was clear/not rusted inside, but I'll double check them

I know that the vented cap may only be a temporary fix, but want to try it anyway since I remember cracking the cap open a bit relieved the issue last time it was ocurring

 

[Steverino]

I did verify last night that my long trunk vent tube is absolutely clear, and there was a few drips of gas inside each of the end of the tank vent outlets, so I'm sure they are capable of venting

I'm wondering if even the incorrect placement of the short and long tank vent tubes could be having an effect ?
Both the old tank I removed and the new one I put in have the long and short vent tubes reversed, I'm wondering if the placement was somehow "precisely engineered" to work the correct way but doesn't allow them to work efficiently when reversed as these new tanks seem to have

I'm going to fill it up again (just under 3/4" now), and see what happens, but am still wanting to try a vented cap if I can find one, or had anyone had success by drilling a small hole in the cap in a spot that will allow it to vent without leaking ?

Thanks

 

[chtampa]

If you have the repop tank with the vent lines reversed on the inside you can just swap the hookup on the outside. The cap isn't going to make a difference.

 

[HT413]

Vent cap will leak like hell from fuel slosh. Previous owner had one on the car when I bought it, leaked a few gallons of fuel on the flatbed home.

 

[Steverino]

I do have the hoses swapped on the outside of the tank

Long outside goes to short inside, and short outside connects to long inside

We'll see how it goes the next time I fill it

If I have an extra cap I could fool around with venting (drilling) that, but I have a feeling I'm going to end up "extending" the shorter external vent with a foot or 18" of hose up into the frame rail perhaps

 

[HT413]

I have a feeling I'm going to end up "extending" the shorter external vent with a foot or 18" of hose up into the frame rail perhaps

If swapping the lines doesn’t work, this might.