The line going up the right frame rail is the delivery line. It connects to the larger of the two ports on the tanks sending unit/ pick up and goes to the fuel pump
On the left frame rail, the smaller line is the fuel return. It goes from the fuel filter return port to the smaller of the two ports on the sending unit. The other line on the left frame rail is the vent line and it goes from the two roll over valves to the carcoal canister.

 

Right on, thank you. Since one of those steel lines is already buggered, is it advisable to replace it with another steel line? Or will a fuel-rated rubber hose be perfectly fine? The prospect of running another steel line with the tub on is not terribly exciting to me. For that matter, why are any of the fuel lines steel if rubber hose is ok?

 

Steel would be less likely to get torn by something when off-roading but if it's tucked up in the frame or out of the way I suppose it would be ok, for a while. Also, rubber hose, if not secured, will rub through and eventually leak in a short while. If I did it and I would try not to, I would use U.S. made fuel injection hose as it is much tougher. But steel is better and Stainless is best.

 

Keep the feed line steel as much as possible if that's the one that's damaged. Rubber retains heat and can lead to vapor lock.

 

Keep the feed line steel as much as possible if that's the one that's damaged. Rubber retains heat and can lead to vapor lock.

I should have been more clear. It is one of the return lines, I just don't know which.

Another related question, why do fuel lines not have the springy rock guard stuff?

 

The wrap isn't there because fuel line isn't subject to the pressures that brake line is.

 

i was experimenting with ways to cure vapor lock - briefly had a new fuel filter between the mechanical pump and carb that had a port for a return (wix 33041 iirc?). I ran a rubber fuel line back down through the frame rail as the return line to the tank.

ended up putting in an electric pump and took out the return line, but posted fwiw if you are looking to run a return line in a safe place. the only downside I could think of by running it inside the frame rail is eventually if a leak occurred it might take a while to notice it - especially if it was small and never got large enough to drip out of the rail ... vapors = bad news since they are what actually ignite.

(the return line kept the fuel liquid, but I think it may have then also contributed to fuel issues by diverting some of the fuel away from the carb back to the tank. I went with the electric pump because with the return line, I couldn't go much above 3k rpm without running out of power)