Fuel Tank Return Line

[Jack21]

Steve,

Assumption is carbureted engine. Fuel injection engines (gas & diesel) have/need fuel return lines.

Unless Murphy just has a thing for you and fuel pumps, I don't think you need a return line for reasons stated. If you look at the way a fuel pump works, you're not pumping against a resistance and prematurely wearing out your fuel pump. If that were the case, there would be a lot of guys (and a lot of lawsuits) with bum fuel pumps.

I do know the feeling though. There's a spot on the PA Turnpike NE Extention called fuel pump rock. Broken body casting. That was a long time ago, and it hasn't happened since.

When the pressure at the carb matches the pump output, the pump stops pumping. Bleed this pressure back to the tank, and the pump then will work harder defeating your purpose.

When you shut the motor off on a hot summer day, particularly if you have AC, the heat from the engine can boil the fuel between the pump and carb causing vapor lock, and excess fuel percolating out of the carb into the intake. Can make engine seem "flooded" (which it is) upon hot restarting. Are you getting something like this? If so, do a fuel return line.

In this case, you need a very small orifice, about a #60 jet size, to bleed the pump-to-carb pressure back to the tank while the engine is NOT running to prevent vapor lock and percolation. Many carbureted engines with AC and were prone to this, had this feature.

Most fuel tanks already have provisions for fuel return lines. If yours doesn't, you want to have the tube near the bottom so liquid fuel goes into liquid fuel. The rationale for this is different, however. Fuel can build up a static electricity charge as it is a poor conductor. The liquid-liquid transfer minimizes this.