Dual Tanks and Fuel Injection

[Nobody]

Dual Tanks and Fuel Injection

What needs to be done for the return line? Do you just plumb it into the main tank? Second valve for the return? Buy a single aftermarket tank?

 

[Steve]

Holley makes an electric switched valve for this exact purpose. It switches the supply and return together so they're always connected to the same tank. I would definitely not plumb it to one tank. Around $100 IIRC. You should be able to find it easily on Holley's web site.

 

[lars]

Depends on home complicated you want to make it. You could say mine's complicated because I'm using a Pollak 6 way motorized valve. It switches feed & return from both tanks as well as switching which sender unit feeds the fuel gage. But it's simple to use now that it's hooked up, and hooking it up was really no big deal. No more floor mounted valve, just hit the dash switch.

I've got a NWMP main tank, it had extra vent tubes welded to it so I'm using one of those for a return on that tank. I've still got the stock OEM plastic aux tank. I yanked the sender unit, drilled a hole through the cover plate and silver soldered a piece of 5/16 stainless tube into the hole to make a return on that tank. Another option is to solder/braze/weld a return tube into the filler neck on either tank. Works just as well.

 

[70_Steve]

Look in BC Bronco's Tech Library for the Fuel System Wiring and Plumbing Diagram.

http://www.bcbroncos.com/fuelsystem.pdf

 

[Nobody]

Thanks! Those electric switch valves sound like the ticket.

Curious, how much fuel gets returned?

 

[SaddleUp]

That diagram is overly complicated and adds unnecessary components into the system. Specifically the low pressure pump and accumulator which aren't needed. (Other than that it looks right except that fuel filters should be used between the tank and fuel pump and then between the fuel pump and fuel rail) If I recall right the Pollak valve Lars mentioned above costs about $59 at Napa. I don't recall the part number but I just told them what I needed and they dug around on the shelf for a few minutes before they pulled it out. For the front tank I did the same as Lars and for the rear tank I added a T into the vent line. BTW, when I was running dual tanks I put the fuel pump (I only run one high pressure pump) right after the switch and mounted it to the frame rail by the front tank.

 

[SaddleUp]

Thanks! Those electric switch valves sound like the ticket.

Curious, how much fuel gets returned?

It is constantly returning fuel any time the pressure is greater than what the fuel regulator accepts. (Basically all of the time) If you try to run it into one tank then you will quickly fill that tank and empty the other one.

 

[chromeyellow]

A/c Delco Has A Fuel Tank Valve That Also Has The Return Ports For About 50 Bucks. If You Want I Can Find The Part Number.

 

[Nobody]

Thanks, I think I can find what I need now. I'm still a ways out from FI. I noticed that my fuel lines are dry rotted, so if I'm going to replace stuff, might as well prep for FI.

 

[edge4]

You can find my tech article on installing twin switched tanks, accumulator, and EFI in the CB Bronco Tech section. I respectfully disagree with saddle up on the sucker pump and accumulator. I pulled air a couple of times into my fuel rail on steep climbs without them. Last place you want this to happen.
Edge

 

[SaddleUp]

You can find my tech article on installing twin switched tanks, accumulator, and EFI in the CB Bronco Tech section. I respectfully disagree with saddle up on the sucker pump and accumulator. I pulled air a couple of times into my fuel rail on steep climbs without them. Last place you want this to happen.
Edge

I seriously doubt that you drive yours up any steeper hills than I do mine. On more than one occasion I have had the front end past the breakover point with the front tires in the air where I had to stop and use a winch just to get up the side. Purred like a kitten every time. Granted I had at least a quarter tank of gas every time so I don't know if that would have been the same case when the tank was really low.

 

[casadejohnson]

I just went to the junk yard today and got a stock ford truck/van valve for Fuel injected vehicles with dual tanks. Now I just need to figure out the wires and put it in. I'll let you know how it works out. The price was right, I only paid $5 for the valve with fuel line to the fuel rail.

 

[lars]

I haven't had a problem with mine, but I did install fuel injection in a Jeep once using the same high pressure pump as I've got. All silliness about Jeeps vs. Broncos aside, the pump didn't know what vehicle it was mounted on, and in that installation if it sucked air or even if the tank got too low the pump wouldn't re-prime easily. A Carter sucker solved the problem. I've heard of EB owners who don't need them, others who had problems till they installed one. Go figure.

 

[SaddleUp]

I just went to the junk yard today and got a stock ford truck/van valve for Fuel injected vehicles with dual tanks. Now I just need to figure out the wires and put it in. I'll let you know how it works out. The price was right, I only paid $5 for the valve with fuel line to the fuel rail.

The stock truck valves or at least the ones on late 80's trucks require a pusher pump on each tank to work. I.E. They are pressure activated depending upon which tank is pushing fuel to them. I have one from an 88 in the garage that I was going to use (It cost me $5 less than yours did) but I opted not to even though I already had the extra pumps because it would complicate a system that already was working very well.

 

[casadejohnson]

The stock truck valves or at least the ones on late 80's trucks require a pusher pump on each tank to work. I.E. They are pressure activated depending upon which tank is pushing fuel to them. I have one from an 88 in the garage that I was going to use (It cost me $5 less than yours did) but I opted not to even though I already had the extra pumps because it would complicate a system that already was working very well.

Sounds like mine may not work then. I was unaware that they were pressure activated. Does your switch have wiring attached or is it just pressure activated?

 

[lars]

The stock truck valves or at least the ones on late 80's trucks require a pusher pump on each tank to work. I.E. They are pressure activated depending upon which tank is pushing fuel to them. I have one from an 88 in the garage that I was going to use (It cost me $5 less than yours did) but I opted not to even though I already had the extra pumps because it would complicate a system that already was working very well.

Not necessarily, though Ford did use a pressure activated setup in some systems. The application for my Pollak valve was an 86 F250, same as my high pressure pump. It's true that the F250 used low-pressure in-tank pumps that were switched by the valve, but they aren't necessary. The internals of the valve I have are identical to the Delco-spec valve. The only difference (which also happens to make the GM valve cheaper and more user friendly due to connector availability) is that Pollak molds the GM valve so it can use a Weatherpack connector instead of Ford's proprietary connector. I've had both types apart on my workbench. They are internally identical. If you have a Ford valve, just make sure you've got the mating connector as they are impossible to get. Here's Pollak's page with all the bits & pieces, including the GM-style valves and corresponding Weatherpack connectors: http://www2.catalognavigator.com/pollak/category/fuel-tank-selector-valves

 

[SaddleUp]

Not necessarily, though Ford did use a pressure activated setup in some systems. The application for my Pollak valve was an 86 F250, same as my high pressure pump. It's true that the F250 used low-pressure in-tank pumps that were switched by the valve, but they aren't necessary. The internals of the valve I have are identical to the Delco-spec valve. The only difference (which also happens to make the GM valve cheaper and more user friendly due to connector availability) is that Pollak molds the GM valve so it can use a Weatherpack connector instead of Ford's proprietary connector. I've had both types apart on my workbench. They are internally identical. If you have a Ford valve, just make sure you've got the mating connector as they are impossible to get. Here's Pollak's page with all the bits & pieces, including the GM-style valves and corresponding Weatherpack connectors: http://www2.catalognavigator.com/pollak/category/fuel-tank-selector-valves

Since I don't recall having any wires attached to mine and it is currently buried I'm going to say casadejohnson probably has one of the pollak valves. Especially if it resembles the ones on the Pollak page. The one I have from the 88 doesn't come close to being the same. It is much larger. If it was handy I would take a pic of both side by side for comparison. (I know right were the Pollak one is since it was only a month or so ago that I took it out) I wonder how many years each side of 86 they used it? That would be the ticket for those doing it on a budget.

 

[casadejohnson]

Well, sounds like my valve is worth experementing with. I'll try to figure out the wiring on it and do a bench test this afternoon. I think I'll set up a gravity feed to the valve and attempt to divert water through it. I'm thinking that water should not damage the valve as long as I get it dry before installing it. It also will be better to use water when I inevetably spill it all over the floor.

 

[casadejohnson]

Well I did some tests and I'm sure that my valve will work. I even figured out the wiring from the valve to the tank sending units. I just have to wire my current switch so that it can reverse the polarity to the valve. It actually works very well and I got all of the fittings that attach to it from the donor vehicle so the install should be easy.

What are you all using to attach your fuel lines to the frame? I'm moving my lines from the inside of the frame rail to the outside to keep them away from the exaughst and I'm looking for a good mounting method.

 

[lars]

Well I did some tests and I'm sure that my valve will work. I even figured out the wiring from the valve to the tank sending units. I just have to wire my current switch so that it can reverse the polarity to the valve. It actually works very well and I got all of the fittings that attach to it from the donor vehicle so the install should be easy.

What are you all using to attach your fuel lines to the frame? I'm moving my lines from the inside of the frame rail to the outside to keep them away from the exaughst and I'm looking for a good mounting method.

I tapped 1/4-20 holes into the side of the frame rail and used Adel clamps for my fuel lines.

I have a wiring diagram from Pollak that shows how to wire everything including the switch (the switch they show in their schematic functions exactly like the OEM Bronco selector switch on your dash- that's what I use as well). I can't find a link to it on their site anymore, but I've got the image saved on my computer. PM me and I can email it to you if you want.