I ordered a new fuel sending unit for my 73 f100, The original has two lines, the aftermarket has one line. I've looked at several companies that sell different brands, and they all have one line for that year truck. If I do have the right part, where do I hook up the return line to? My tank has 3 lines altogether, going to the tank, send, return, and the vent line. Am I missing something here?
original one, two lines

New one, one line

 

Have you looked at the part for 72 and/or 74 model years? Yours could be a mid year change or something??

 

That was one of my initial thoughts also. I checked both years 72 & 74, the fuel sender is the same part # from 73-79. 72 had the tank behind the seat from what I read online. I'm just really stumped on this issue, I've gone to Autozone, Oreily's, Merles, Napa, and every store carries the same, single line fuel sender, even the online stores. A guy at one of the stores mentioned that it might have been a "built in Canada truck", That the Canadian vehicles are different from the USA models. I'll have to look into that. I'm taking a trip down to El Paso, TX, to visit family for the weekend. I'm gonna try some Texas stores, and see if they just might have the two line sender.

 

Ive also been thinking on this. Follow the hose that is extra on that sender. Im thinking it may not be a return at all. Maybe a spill collector from the gas neck? Some kind of vent? If it was a return it would have to run up to the fuel pump as a bypass.

 

My truck has a return line, no doubt. Here's pictures of the lines going to the carb. It has the two lines on the sender, and one line on top of the tank for the vent valve line that goes to the charcoal canister.

 

I still can't find a two tube sender anywhere. The closest I got, was a 1974 sending unit from a Ford Thunderbird, that's very similar to what I have. This is not making any sense to me at all.