Fuel return line

[Okiedokie]

So you all have educated me as to the value of a return line to the tank and imersed in fuel in the tank. However, since it is impractical to install a return fitting in the tank, would I just be spittin in the wind to tee into the fuel supply line between the tank and the electric fuel pump and return the fuel there? Joe

[wayne petty]

how about a bulk head fitting through the tank next to the sending unit hole... where you can reach it.. with the jam nut on the outside...

install the intank return line section on the short side of the bulk head fitting..  stick it into the tank through the sending unit opening.. stick the jam nut on and tighten it..  reaching through the tank opening with a long wrench to hold the inside while you tighten the jam nut..

then you can install the tank with the outer return line fitting easily..




you can also do the same thing  if there is any room on the sending unit..

one thing.. if you are creative..  you can take the sending unit... drill a small hole..   work it with a tapered punch backed up by a drilled rod to keep the flair straight.. flare the flat to a necked flange.. then tin the opening with low melting point silver solder.. tin the tube where you want it to stick..  slip it in.. silver solder it into place..    there is low melting point silver solder in small coils with liquid boric acid as a flux in a squeeze tube with it.. for under 10 bucks...   strong stuff..  i use it to solder a LOT of stuff.. including friends eyeglass frames..  with the lenses out..    i use my normal weller solder station..  or the MC tank and turbo torch...

[enjenjo]

I just did one similar to what Wayne suggests, I silver soldered a return line into the fuel sending unit cover, bent the return line so it was right along side the tank float so it would fit into the tank. You can also use a bulkhead elbow, and install it in the filler neck.

[Okiedokie]

Thanks for the tips guys.

[taxpyer]

Okay guys,,, :?  I just finished putting a 1982 2.3L Ford motor in my CJ2A and it has a return line provided for off the fuel pump.  I just blocked it off :oops:  and so far all seems to be fine.  Will it ruin the pump or over pressure the carb? :?

[wayne petty]

this 2.3 has a mechanical fuel pump mounted on the block right...

 it won't hurt the pump... it should not over pressurize the carb fuel inlet..

but you might check the fuel pressure..

the return line on later model pumps reduces vapor lock problems..

fuel pumps cannot pump vapor..   so letting a trickle of fuel return to the tank lets the pump circulate fuel and any time vapor builds up from heat soak.. or up long hills ... it is send back to the tank in the return line..


the reason that electric fuel pumps need a return line.. they are designed for pressure ranges... and flow rates...   they DO NOT HAVE internal spring loaded  bypass valves to limit pressure like an engine oil pump has..  

dead heading a conventional OEM intank fuel pump  causes it to run slower...  draw more current.. over heat the tiny brushes as they were not designed for dead head pressure/current draw levels..

aftermarket electric pumps like the holley blue and red pumps have a spring loaded internal pressure relief valve..   this valve dumps flow when the pressure builds up..  it dumps it back into the pump inlet..

this is one of the drawbacks and why some people hate these pumps.. they refuse to run a really good filter before the pump inlet..   any debris from the tank or lines that gets sent through the pump can jam the pump relief valves open.. letting the pump freewheel...  and not being able to build any pressure to fill the carbs...

the advantage of an internal spring loaded relief valve.. you can limit the pressure and really not have to run much of a fuel pressure regulator...

some electric fuel pumps for cars are designed for well over 100 psi...  these are the 250 to 300 buck pumps..    usually not in tank.. and gravity feed or with booster pumps to feed the high pressure pump...

look under a mercedes 190... from the late 80's.. they had 2 pumps and a big accumulator..   one pump filled the accumulator.. the other took that fuel and really built some pressure with it..   these were for mechanical fuel injection systems.. bosch CIS..  and its variants..

newer cars have no return fuel injection systems.. but the pumps and regulators are in the tank...    some cars.. i think the newer corvettes have a pressure regulator and return line built into the filter and thats back by the tank..

do to the electronic pulse width modulation available now.. some OEM manufacturers are using that to control fuel rail pressure by modulating the power to the pump ...

oh.. and for those people with newer cars..  when you go to look for the fuel filters and cannot find them..   they are hidden inside the tank on the pump module...   so instead of a 10 or 20 buck fuel filter to replace..   now you have to drop the tank and change the over 300 buck fuel pump module..    another good reason to build and drive older cars...


sorry if i went off thread slightly..  i thought it needed saying..

did i get anything wrong?

[GPster]

Could he weld/braze/solder a short piece of steel line in the fuel tank fill pipe (if it's removable) and run his return line to it? When he had the fill pipe off to do the modification he could put a piece of hose on the small line on the inside of the fill pipe that would go into the tank inside the fill pipe. The hose could be long enough so that the loose end laid on the inside bottom of the tank so that it would remain under the tank's fuel level (unless the tank was empty). Might be safer working on the fill pipe rather than the tank. Unless I'm missing something this might work. GPster

[Mac]

I've read that a return line should extend down to almost the bottom of the tank, thereby remaining submerged. They say there's a potential for static charges with a fuel return just pouring back into the tank.

[Okiedokie]

Good idea GPster. I will look into your idea. Thanks, Joe

[model a vette]

"Could he weld/braze/solder a short piece of steel line in the fuel tank fill pipe (if it's removable) and run his return line to it?"

That is how GM did it on turbo and then later smogged Corvairs.

[GPster]

"Could he weld/braze/solder a short piece of steel line in the fuel tank fill pipe (if it's removable) and run his return line to it?"

That is how GM did it on turbo and then later smogged Corvairs.

Never had a turbo Corvair or one new enough to be smogged. Every time I think I have a good idea someone else has thought pf it before or Wayne knows a site with pictures on how it's done. GPster