re-installing an Aux Fuel tank after EFI install

[thomaspadden]

Im a novice and have some mechanical ability btw.

So i have a 1972, 302, 4 speed manual trans beauty! Love her to death. I had a mechanic install a Holley Sniper EFI. I removed both the old fuel tanks, main and auxiliary. I had them install a 23 gallon from Toms bronco parts with the in-tank high pressure fuel pump for the Sniper. It has a return line to main tank.

I want to reinstall my 9 gallon Auxiliary Tank and have it dump into the main tank. This is what i was thinking on how to do it.

Run the 3/8 fuel line from the Aux tank and "T" into the return line from the Sniper EFI. I called Holley and they said that the return pressure is approx 4 psi to the main tank. I was going to use a "dash switch" activated low psi inline carb pump (mounted to frame) to pump from the aux tank to Main tank when the main tank got to 1/4 full. I still have the fuel gauge switch on the dash to be able to switch from one fuel gauge to another so i know how much each tank will have.

Ideas? Will this work? anything im not thinking of?
Plain Talk for me please im not very techy.

 

[Broncobowsher]

I would start with just driving it with the 23 gallon tank. Most people find that sufficient enough that it isn't worth putting the aux tank back in.

One of the things I don't like about your plan or most any transfer pump plan is getting the pump turned off so you don't burn it up. Fuel pumps in general are not happy if you let them run dry. It takes a surprisingly long time for a regular fuel pump to transfer even that small aux tank. It would be real easy to forget to turn the transfer pump off. When I did this I had it setup with an external pumps. It would pull fuel from either tank but only return to the main. If I ran the aux tank dry the engine would stall, switch back to the main.

You could do a variant of that. High pressure pump pull from the aux and Tee into the supply line. If you run the aux out of gas, engine stalls. All return goes to main. Even then care must be used to avoid overfilling the main tank. It would be too easy to run out on the main, flip to the aux, roll into a gas station, get distracted filling the tanks, leave with the aux tank overflowing the main tank. And yes that does happen.

 

[BroncoChicken]

You can use the fuel gauge selector switch to activate the LP transfer pump. Switch to Aux, the gauge reads the level in the tank and turns the pump on. When it’s almost empty, switch back to Main and the pump turns off and gauge switches back to reading the Main tank level.

Looking at the back of the switch:

Main Gauge Aux

Empty 12v AuxPump

 

[.94 OR]

I just set mine up to do the same thing.

TBP 23 gallon in-tank EFI pump to my FiTech with return line. I plumbed the aux tank back into the vent on the pump. It has worked so far since the tank itself is vented up to the fill point.

I used a small low pressure electric pump with a low pressure cut-off switch. I wired up two switches, the first an on/off (illuminated) and the second a momentary on (illuminated) to power the pump. By turning the main switch "on", it would provide power to the pump through the cut off switch. Since there is no pressure to allow the pump to start up I activate the pump with the momentary switch until pressure is high enough to run automatically. Release the momentary switch and the system runs until it runs out of fuel at which time the pressure switch kills the circuit and the illumination light on the switch goes out letting me know its done. I printed the switch mount to go under the speedometer to house my air locker switches and the two push button fuel transfer switches.

 

[spap]

I am in the same boat toms wild horses or toms 23 gal tank. In tank pump. Fuel injected Lo po 5.0
Thanks for all the ideas.

I was wondering about doing the aux tank with a separate high pressure fuel pump mounted on the rail to tie into the high pressure fuel line already supplying the fuel injection

More of a safety measure in case the main in tank fuel pump craps out , I would have a back up. I like to keep things simple don’t like getting stuck in the middle of no where

Are there potential problems with that set up ?

 

[66BlueGoose]

Add a one way check valve coming from your Aux Tank to ensure your EFI return doesn't dump fuel back to the Aux tank, just back to the main.

 

[jamesroney]

I am in the same boat toms wild horses or toms 23 gal tank. In tank pump. Fuel injected Lo po 5.0
Thanks for all the ideas.

I was wondering about doing the aux tank with a separate high pressure fuel pump mounted on the rail to tie into the high pressure fuel line already supplying the fuel injection

More of a safety measure in case the main in tank fuel pump craps out , I would have a back up. I like to keep things simple don’t like getting stuck in the middle of no where

Are there potential problems with that set up ?

You will have to figure out how to prevent back-flow from your aux tank pump into you main tank. Assuming that you are running your aux pump because there is something wrong with your main pump...The fuel pressure regulator will put 40 psi on the rail, which means 40 psi pushing back on your main tank fuel line.

Also need to figure out the return line as noted. The bypass regulator will dump fuel back into the main tank at a pretty good rate. I would guess that it will empty your 7.5 gallon aux tank in under 30 minutes.

 

[jamesroney]

Im a novice and have some mechanical ability btw.

So i have a 1972, 302, 4 speed manual trans beauty! Love her to death. I had a mechanic install a Holley Sniper EFI. I removed both the old fuel tanks, main and auxiliary. I had them install a 23 gallon from Toms bronco parts with the in-tank high pressure fuel pump for the Sniper. It has a return line to main tank.

I want to reinstall my 9 gallon Auxiliary Tank and have it dump into the main tank. This is what i was thinking on how to do it.

Run the 3/8 fuel line from the Aux tank and "T" into the return line from the Sniper EFI. I called Holley and they said that the return pressure is approx 4 psi to the main tank. I was going to use a "dash switch" activated low psi inline carb pump (mounted to frame) to pump from the aux tank to Main tank when the main tank got to 1/4 full. I still have the fuel gauge switch on the dash to be able to switch from one fuel gauge to another so i know how much each tank will have.

Ideas? Will this work? anything im not thinking of?
Plain Talk for me please im not very techy.

Make sure that you buy a transfer pump that is rated for continuous duty. Most fuel pumps for carbureted applications are not designed to actually flow fuel. they normally handle about 5-10 gallons per hour. (figure 15 miles/gallon @ 60 MPH = 4 gallons per hour.)

There are lots of good pumps out there that can handle the flow, and are self cooling. But some are not...and get super hot even when pumping fuel.

 

[Z Bronco]

I have my auxiliary tank line going into a Carter external fuel pump mounted on the frame, then into a Napa Check valve (Carter) to stop back flow, then through a tee into the return line. This works great. Before I installed the check valve, fuel would back flow into the auxiliary tank. I also have a safety switch on the dash to prevent accidental fuel transfer. My EFI tank is 23 gallons, and my auxiliary tank is 12 gallons. The aux tank with this set up is really just a big fuel can. On my cross country travels combined with remote wheeling and exploring, I have used every bit of those 35 gallons.

 

[OX1]

Im a novice and have some mechanical ability btw.

So i have a 1972, 302, 4 speed manual trans beauty! Love her to death. I had a mechanic install a Holley Sniper EFI. I removed both the old fuel tanks, main and auxiliary. I had them install a 23 gallon from Toms bronco parts with the in-tank high pressure fuel pump for the Sniper. It has a return line to main tank.

I want to reinstall my 9 gallon Auxiliary Tank and have it dump into the main tank. This is what i was thinking on how to do it.

Run the 3/8 fuel line from the Aux tank and "T" into the return line from the Sniper EFI. I called Holley and they said that the return pressure is approx 4 psi to the main tank. I was going to use a "dash switch" activated low psi inline carb pump (mounted to frame) to pump from the aux tank to Main tank when the main tank got to 1/4 full. I still have the fuel gauge switch on the dash to be able to switch from one fuel gauge to another so i know how much each tank will have.

Ideas? Will this work? anything im not thinking of?
Plain Talk for me please im not very techy.

I did exactly that with stock tanks as I think the dual tanks are cool.
Stock fuel switch just so happens to be DP DT, so I wired the transfer pump to be on only when I switch fuel guage to front tank.
My replacement plastic tank had an extra "bung" that's probably for a vent (I still have vented caps) that
I used to keep EFI return, and the transfer inlet separate.

 

[redleg45]

I am using a four port electronic valve to switch from tank to tank. Both tanks have their own high pressure pump and return to each respective tank. The gauge reads the tank being used. Make sure the pumps put out the same pressure/volume so you don’t have tuning issues (ask me how I know �&#56846.

 

[blknblu69v]

I have my auxiliary tank line going into a Carter external fuel pump mounted on the frame, then into a Napa Check valve (Carter) to stop back flow, then through a tee into the return line. This works great. Before I installed the check valve, fuel would back flow into the auxiliary tank. I also have a safety switch on the dash to prevent accidental fuel transfer. My EFI tank is 23 gallons, and my auxiliary tank is 12 gallons. The aux tank with this set up is really just a big fuel can. On my cross country travels combined with remote wheeling and exploring, I have used every bit of those 35 gallons.

How long does it take to empty the aux tank into the main tank?

 

[Z Bronco]

I have never timed the transfer, so I am not sure. I usually am stopped someplace enjoying the scenery, so my guess is a few minutes.