Fuel line question

[Hair]

I have a 71 GMC that came with an I6, putting a 1988 carbureted 454 in it. I am in the process of hooking up the fuel lines to the pump. The pump has two lines out the bottom and a connection out the side which goes to the carb.

My tank has two lines coming out the bottom thru the cab floor:
- One runs up the frame to the pump, I'm sure that's my fuel delivery line.
- But the other line is a rubber hose about 12" long and it is just hanging back there under the cab. Looks like its been hanging there like that for years.

Question: Do I need to run that other line up to the pump and hook it to one of those tubes out the bottom of the pump?? Or do I put a nipple on one of the pump lines to plug it off, and just leave that old hose hanging back there, maybe its a vent or something??

Also, concerning the two tubes out the bottom of the pump, does it matter which one I hook the fuel line to??

[wake328]

one of the nipples on your pump should be noticeably larger, thats your fuel inlet. The smaller one is a return line. The line hanging there could be for the fuel return.

I am sure someone can correct me... but i'm not sure on the 71 if they had the 3rd line as well for the charcoal canister?

[Hair]

There's no third line that I can see any where.

[Hair]

Ok, I ran the fuel line to the big nipple on the fuel pump and left the small "return" nipple alone unplugged with no hose. I finally fired the engine for the first time today. Squirted some fuel down the carb and it fired up and ran a few seconds, did this several times. Fuel started pouring out the fuel pump nipple that I did not run a hose to, the line going to the carb is as dry as a bone. Any idea what I have wrong?? I can run the return back to the tank, but is that going to make it pump fuel to the carb??? I thought he vent line really didn't matter. Help please.

[Hair]

I put a nipple cap on the open nipple, started it and it sent fuel up to the carb and it runs great now. SO now my question is, should I run that line back to the tank or just leave it plugged?