carb questions- return line required? (1 Viewer)

[F-junker]

I have a 79 carb and engine with no return line just a bolt in place of the banjo fitting. the truck I put it in has a fuel return line in the truck, of course the tank I had restored has no return fitting.

DO I NEED A RETURN LINE??? what would the positive and negative effects be?

I'm rebuilding a non-USA spec carb circa 76', I will plug off the return port on the carb if I don't really need it. I figured it was an emissons thing an "E" thang!
Thankfully, I don't need to worry about any smog detail as I'm under historic registration and this thing will only be a toy.

 

[alf]

I have a 79 carb with no return line.

I believe the return line on the 79 was at the fuel pump not at the carb. With that said my return line is capped at the fuel pump as well with no ill effects.

 

[Pin_Head]

I can't see this being an emission thing, and you can be sure that Toyota doesn't put something on there for no reason. I'm not sure what it does, but some guesses are that it limits the inlet pressure and by circulating the fuel it leads to lower fuel line temperatures and less chance of vapor lock.

 

[Mr. Toad]

I can't see this being an emission thing, and you can be sure that Toyota doesn't put something on there for no reason. I'm not sure what it does, but some guesses are that it limits the inlet pressure and by circulating the fuel it leads to lower fuel line temperatures and less chance of vapor lock.

I also think that the return line keeps the entire pressurized system--from pump to carb--at the level it was designed to operate at. I imagine that the fuel pump diaphram can't be too happy trying to pump up an over-pressurized system.

 

[Toyo FJ40]

There's been a few posts about fuel boiling in the pump with the return line blocked.


Kevin

 

[F-junker]

At this point I believe I may try and fit and return line and plunb it through on of the vents in my gas tank, thank you all for your input.

 

[desertpat]

Fuel Lines

I had a '75 2F and now have newer FJ's ('83 and '84) - all non USA. The '75 had a supply to the carb and a return. The newer FJ's have only a supply and the return function was in the fuel pump. The fuel pumps were different.
I can send a Toyota drawing of the later versions - the older version fuel pumps had a lots of screws / bolts - the newer version fuel pump is molded with three ports.
hewitt_pat@hotmail.com (desertpat)