Carb fuel return line

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sggoat

sggoat

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Searched through the FAQs and others to find info on carb fuel return lines with no luck. Maybe someone can help--Just finishing the rebuild on an Aisan carb to replace the weber I currently have installed. My truck is a '77, the carb(I think) is a 75-based on the mfg date of May 27 1975(5E-27)-carb number is long gone.
My fuel pump has three connections--one suction from the tank, one return line to the tank, and 1 supply to the carb. My question is: where should I route the return from the carb? Does it need to go all the way back to the tank(and if so, where would it enter), or could I just tee into the fuel pump return line?
Thanks for any help
Gary
fuel pump connections.webp
 
The 3 tube pump is designed to work with later carbs that lack a fuel return line. If you have a 3 line pump and a carb with a fuel return, plumb the carb return into the pump return with a T fitting.
 
Don't know why the fuel pump is what it is--came that way to me. I think the original Aisan carb had the return plugged as Fast Eddy says. Replaced the original with a Weber(no return) now I want an original back on it. The carb I have is from a 75(I think), but does have the return. I was thinking just as you, that the constant flow of fuel would at least lessen the chance of boiling causing the dreaded v-lock. My only concern would be if I hooked it up as Pin_Head says, could there be return line pressure build up from the pump enough to stop(or slow) the flow from the carb?
It almost sounds like the best course would be to plug the pump return and tie in the carb return to the tank through the pump return line. I don't know if this configuration would hurt the pump, though.
Does this make any sense?
Gary
 
I had a '79 and later 2F with a 76 carb and the carb return was joined with the pump return with a T at the pump. It ran fine that way for 15 years. Get an early "screw top" fuel pump with only an inlet and outlet and then you can plumb the carb return back to the tank like it was on a stock '77.
 
I think I like the "T" solution-sounds reasonable. Will do. Thank you very much. Will follow up later on results.
Gary
 
Have a similar problem with a later model 2F fitted to a '71, with the return on the fuel pump but no return line to the tank.
Can i tee the return hose back into the pick up line from the tank or will this cause problems?
 
No, do not tee it back to the fed line. Tried this and it didn't work. The pump just ends up recirculating airbubbles/fuel in from the return fitting.

Either cap off the return at the pump, or take the return all the way back to the tank and dump it into the top of the tank by adding a tee fitting in the fill breather hose.
 
Will the fuel pump last if i cap the return off?
I have the old 'F' fuel pump that came in the spares pile, but the fitting has been over tightened and cracked the housing.
Will block off the return for now to get it running.
 
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