Fuel pump bypass function

[Bonnewagon]

Some fuel pumps have two fittings and some have a third fitting for the bypass back to the gas tank. I was curious how it worked. Is there a set volume of fuel that goes to the carb and tank? Or is there a pressure limit for the carb line and any excess goes to the tank? If it works on pressure then on a two fitting pump where there is only one line going to the carb then how does that handle excess fuel? Is the pump regulated? If the float got stuck shut then would all the fuel get bypassed to the gas tank? Then if you plug the bypass fitting I know that the carb will flood slightly, so why is that if it is regulated?

 

[Clone TIE Pilot]

The GM service manual explains that the pump circulates fuel from and back to the tank. A valve in the pump bleeds off fuel to the carb on demand. This valve is spring loaded and normally closed. The idea was to keep the fuel cool and avoid vapor lock.

 

[Bonnewagon]

So it maintains a specific pressure to the carb, and the rest goes back to the tank? If the carb line was blocked would all fuel then go to the tank? I understand the purpose but I don't get how the pump actually functions.

 

[84cutspreme]

as far as i know there is diaphragm and spring to achieve pressure setting. Pretty similar to how regulators would work