Recirculating Return Line Fuel?

[NeverHave-I-Ether]

I have a 93 F250 which I deleted my side tank on. I'm plumbing the fuel line from the aux tank to the selector. A problem posed though is how to return the negative fuel line. I only have on valve on the aux tank. Is it possible to T the return line back into the positive line before the fuel pump? Once the air is out I don't understand why it should be an issue. The pump would pull fuel from the aux tank and the return line fuel would be recirculating in current. I have this drawn out to help explain.

My main concern:
1. Flow, would this cause pressure differences or problems?

2. Air. Will I experience problems with air bubbles from the injectors return recirculating back into the fuel pick up line?

What do y'all think?
Thanks,
Wheeler

 

[NeverHave-I-Ether]

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[Farmer Rock]

If I understand correctly, you are running the truck off the rear tank with the valve switched to the rear? If so, all you have to do is plug the return for that tank like the supply.


Rock

 

[NeverHave-I-Ether]

No, I am keeping the rear tank and replaced the side tank with an auxiliary tank that I would like to plumb to the selector. I ran a filtration system on the frame and don't have the space for the side tank anymore.

 

[Farmer Rock]

Ahh. I see....well, in that case you really should run the return back to the auxiliary tank.
I have to imagine that there will be back pressure on the return side, which would probably over fuel and run like crap if the pressure isn't enough to leak out.



Rock

 

[IDIBRONCO]

Here's another suggestion. Instead of trying to plumb an aftermarket tank into your system to work just like the stock one did, you could use a separate electric pump to pump fuel from the aux tank into the stock rear tank. No return line needed, also no need to switch tanks.

 

[NeverHave-I-Ether]

That's a good idea @IDIBRONCO, running WMO/ATF so I need the separate tank. May end up having someone weld a second valve in. Or figure out how to attach one

 

[TNBrett]

How big is the port in the Aux tank? Is it at the bottom, or at the top with a straw?

If the fitting is say 1/2”npt at the bottom of the tank, I’d just put a tee there for the return. Any air would escape to the tank that way. If it’s in the top, I’d be hesitant because I’d be afraid any air would get trapped in an endless loop, as air bubbles wouldn’t travel down the pickup straw.

 

[Booyah45828]

Need to return the fuel to the tank. Even if the system is "completely sealed", air will still find a way in eventually, and a circulation system like you have will never remove the air from the system. Plus, with your design, I feel filter changes would be a real biotch.

Something that you've overlooked, is that the bypassed fuel is also a cooling feature for the injection pump. With it constantly circulating like that, it would heat up a lot more then it would in a normal return style system, which would be detrimental to pump life.

 

[NeverHave-I-Ether]

Many good points. The air seems to be the biggest issues especially with filter changes. I will not recirculate the fuel knowing this now, and will return the fuel to the aux tank.
Does anyone have links to a valve? Compression valve to bolt on to the tank? Can't find any easily, and I lost my link.

 

[rwk]

Try a search for a bulk head fitting.

 

[NeverHave-I-Ether]

Try a search for a bulk head fitting.

That's the exact key wording I needed thanks! I was searching for "aux tank compression valve" lol

 

[The_Josh_Bear]

Try a search for a bulk head fitting.

That's the exact key wording I needed thanks! I was searching for "aux tank compression valve" lol

Just make sure to get one with Viton seals or find them separately. Then you'll never have to worry about it swelling/wearing out. Rubber won't last long with your alternative fuels.

 

[NeverHave-I-Ether]

I ordered one that has npt threads and uses two washers as seals. I had read of it working for people. Don't like the rubber for reasons you mentioned.

 

[NeverHave-I-Ether]

Ok, I have my hard adapter. Now here's my next problem. Trying to run the return line to my aux tank, how do I bolt it on? It's a nut on one side, so I can drill it out, but I can't get my arm to reach in there! Only thing I can think of is using a grinder to cut out a square, then bolt it on and weld it back up. I don't know how to weld though....

Dang, any idea on how to get it on?