I would like to know if there is a return line for gas on a 1979 Ford F100 with 302 engine. I dropped my gas tank to replace. I was trying to trace a line which I think is the return line. It starts from the top of the gas tank, goes along side the frame and ends in the cab. But it is just dangling free in the cab. Does not attach anywhere. Where is this line suppose to go?

I already figured out that on the side of the gas tank is the filler and the breather. On another side is the hole for float and gas line. On the top there is a hole, which I presume is the return. That's the one which does not go anywhere!!

Need your help on deciding where it should go ! Or if I can just plug the hole ! I need to drive down to Kansas city soon and so I need my truck back on the road ! Help guys ! Help !

 

There shouldn't be a return line on that year truck. Most likely this is the line to the vapor cannister, but I can't imagine why it would go into the cab. It should go to the front right side of the engine bay.

 

I do not see the line hooked up to any vapor cannister. Is that something I can buy at local auto parts store and install real easy?

 

I agree with Ford_Six, it's your vapor line.

When you say in the cab do you mean where you sit inside or up under the cab by the engine?

If it's just dangling free then it's not hooked up to the canister. The canister mounts to the frame below the battery on the passenger side, way down by the bottom of the radiator. The canister is filled with some sort of charcoal to absorb the fuel vapors from the tank. When your engine is running a line coming from your engine to the canister sucks out the vapors to be burned.

The vapor line also allows your gas tank to vent. As your fuel level drops it is replaced with air through the vapor line. If this line is pluged it will develop a vacuum in the tank from the fuel pump pulling gas out of the tank but no air being allowed back into the tank. Once your fuel pump can no longer draw against the vacuum your engine dies from lack of fuel. Older vehicles without a vapor recovery system have a vented gas cap to prevent this. It can also be very hard to remove the gas cap if the tank us under a lot of vacuum. If you plug the vapor line you will need a vented gas cap. You can do this if you need to use your truck right away and worry about the canister later if you don't have one. Or you can just tie off the vapor line up out of the way for now. Hope this helps.

 

Thanks for your help guys. I replaced my gas tank and reconnected the vapor line as it was previously. When I said cab, I meant underneath the cab. I am sure I do not see any vapor canister under the battery, but I see two cannisters, one on each side. I will find out what these cannisters are for - maybe one of them is a vapor cannister that the previous owner removed from its location and is now sitting by the engine.