Fuel return line to tank

[rednexx]

Is this actualy needed? The reason I ask, is that I'm doing a 7.3 IDI swap into a old school 460 gasser.
The gas pot has a fuel switcher, but doesn't have any return lines (carburated) and no provisions for it on the fuel tanks.
I run large generators all day (old doitz diesels) that don't have returns back to the tank. They return to the filter housing only with no problems. They are fed with a Carter electric that probably out out 7-9 psi.
The manual pump on the 7.3 would do the same (I think) as a manual on a gas pot, and just pump all they can and bypass internally.
I'm just trying to figure out if I have to drop both tanks and put return line in and change over the switcher to a return style also.

Thanks for the input in advance!

[cdnsarguy]

The returning fuel was/is used to cool the IP and injectors so I would say it is required to return to the tank(s) ......... the lift pump does not to my knowledge bypass internally. Our system is a completely sealed circuit.. tank to pump/engine and back to tank. Pump handles 28 GPH at 4-6 PSI in a complete circle.

[rednexx]

Thanks cdnsarguy. On a manual or electric fuel pump without a return, they must bypass internally or they would quit the first time you dead headed them (I would presume). So, if I ran an elecric pump without a return, do you think it would be a problem? I also have a Hino diesel that has a manual pump and there is no return on it also.
I can understand the cooling issue to a point, but the superduty's actually heat the fuel in the filter body.
I'm just trying to get out of a lot of mods that I may have to do.

Thanks again

[arthurgoboom]

The return to tank is also used to flush any air bubbles out of the fuel line before they reach the injection pump. It's supposed to be free-flowing, if you connected the return only to the filter head nipple the entire return system would be under 4-6 psi.

As for deadheading the pump, the mechanical pump will just not let the diaphragm spring decompress if the line is overpressured. The pump actuation arm will just float free. Any diaphragm pump (electric or mechanical) can handle deadheading just fine. Vane/gerotor pumps like a holley don't like it though.

[rednexx]

Seeing that the Fuel filter system is alreay being fed at that pressure, and you are only feeding it back at the same, would it be any problem?
The only drawback I can see is that it would be tough to bleed the system if you ran out of fuel.
It's happened to me a few times on my rigs, and it can take a while for them to clean up.

[rednexx]

Anyone else have any ideas/thoughts/input on this? I'll probably be dropping the tanks anyway, but just curious if it is really needed.
Thanks for the input.

[danngreen]

I've only heard about looping diesel instead of using a return, havent seen it or tried it, but the SVO guys say its a bad idea because the fuel will get too hot which causes something called "low lubricity". the return gives it a chance to cool. good luck.