Gas tank vent question

[jason340]

Is the gas tank in a 73 Cuda self venting? It seems to building pressure when it sits out in the sun. I thought it would vent through the series of hoses in the upper front of the tank. Thanks in advance for the help.

[Super Blue 72]

I'm not sure if it's self venting or if it vents through the emission canister.  But was wondering, if you take off the gas cap on a hot sunny day is there a "whoosh" of air that comes out of the filler neck?  I was wondering if your cap is vented or not.  When I put on a locking gas cap I had this issue and driller a small hole in the gas cap sealing gasket.

[hooD]

The 4 vent hoses in the tank will vent it if they are connected properly.  Look to see if they are connected to the vapor separator and not plugged.  Do you have the charcoal canister under the hood...and is it vented to the carb?

[nqkjw]

Hope no one minds if I hijack but it is on topic.
I'm currently building a 72 Dart Swinger and deleted the charcoal cannister.
There is only one vent port from the tank and none in the filler neck.
Where would be the best advisable place to route the vent tube and where to vent it to?

[jason340]

There are 4 hoses connected to a "block" at the rear of the car near the gas tank and i believe a single hose comes out the other side of the block but no canister under the hood. I have not followed the single line to see how far and where it goes. Should it bleed without the canister?

[burdar]

The canister is called a vapor separator.  The single line coming off of it goes up into the engine comp and is connected to the charcole canister.  That is how the tank is vented.  The gas cap should not be vented.  There is a valve inside the vapor separator.  If it's rusted shut, the tank won't vent.  Make sure the separator and all the vent lines are free and not plugged.

If you don't have the charcole canister hooked up, all your doing is venting the tank into the engine comp.  I suppose there is a chance those vapors could ignite but I know a lot of people run without them.  The job of the charcole canister is to store those vapors and allow the engine to burn them...instead of venting them into the atmosphere.
 

[jason340]

Thanks for the pictures and the info. They are a big help.

[Gumby]

What does one do if the separator is missing? I've read they are not reproduced. I had to plug all the vent tubes on my tank.

[burdar]

Then you need to use a vented gas cap.  I wouldn't fill your tank completely full either.  The separator also acts as an overflow.