1986 351w vapor lock/return line
 

Starting to think my fuel problems are this: Original fuel pump had 2 inputs, new one has 1. I, not realizing a problem, simply hooked up 1 line to the pump and left the other.

Is it possible that I'm vapor locking or, something else, due to not having a return line in place? Or, can I just plug the return line?

You are starting thread after thread, and it's all not connecting together. If I remember correctly, you are the one with the weird piece that was in the fuel system? And there was a recent thread today where you said you have two lines, a blue one and a clear one.

I don't think anyone is clear on what this type of fuel system is. I have never heard or seen one like it(which doesn't mean anything) but I don't remember anyone else saying what this setup was either.

If you go back and bring all the threads together with one thread, with a picture of that diaphragm piece, and a complete description of the system, maybe someone will have seen it before.

For instance the two fuel lines; They run all the way to the tank? Or did they run to the mystery piece and then to the fuel pump? Have you ever looked your model truck up and see if they offer a fuel pump with 3 hook-ups? What does your emissions sticker say? It might have something special listed on it.

the 2nd line should be a vapor return line ! part of the emissions garbage !

Fuel issues
 

Gas 351W Holley 4180 carb

The fuel line device I surmise is a check valve and have kept it out of the
system for now but will probably put it back in. Today I took the fuel switch box out and it did drive home, got good and warm.

I didnt know that there was a choice of fuel pumps, the parts store didn't ask, and I hadn't taken mine off first. I should have taken mine in, gotten one with 2 lines input, and this would all be moot.

I guess at this point, the biggest question is - without a return line (not emissions, but return line to the fuel pump) will this truck run properly?

The emissions line is intact.

Like I said, I haven't a clue what system you have. The only system I am familiar with that has return system was on some of the 460's. It had electric fuel pumps in the tanks, with a return line system that started at the carb.

I don't know if they really did have a choice of fuel pumps, I just suggested you investigate this possibility. I am guessing even if you do figure out what this system was, the victory may mean nothing if you can't get parts for it anymore, and you may end up converting it over as much as possible to a conventional fuel system.

Fuel system
 

What do you mean 'conventional'?

Regular tank sending units with a single fuel line connection. Single fuel line running from each tank to a regular tank selector with a single switching wire hook-up(to get the truck running I would first skip the selector valve and just use the front tank). Single metal line running up front with a short piece of rubber to the fuel pump, and then the factory steel line running from the fuel pump to the carb.

Fuel systems
 

Truck had 2 tanks. Front tank pickup totally rusted out. got a replacement diesel tank. Entirely took rear tank and lines out.Left the switch unit in until today, now it's all working on 1 line and i've capped the return. No need for 2 tanks and I see no reason to stop using it this way.

Original lines were all hard plastic. Now some rubber lines as needed. I may redo the rubber line above the fuel pump, but see no reason really. Is there one?

Maintenance reasons mainly. Rubber lines get old an rot/leak, especially around the heat of the engine. The steel line will last the life of the truck.

Gas line
 

Makes total sense. Definitely will do.