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Dual Tank Systems

Discussion in 'Early CJ5 and CJ6 Tech' started by Steve's 70-5, Jan 4, 2021.

  1. Jan 4, 2021
    Steve's 70-5

    Steve's 70-5 Active Member 2020 Sponsor

    Louisville, Ky
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    Installing a rear tank on my Jeep, kicking around how I want to switch from tank to tank. Did some research on the forum and there where two ways they switched tanks. The threads were a few years old and I have ,I think, a new twist on what was done. I am installing a EFI system on my Jeep and I am using a FiTech Force Fuel system to supply the TB. The way I am doing this, I can use a low PSI In-line pump, the Force Fuel will increase pressure for the TB.

    One way was the brass six port valve that switches fuel flow. If using a inline fuel pump, there will be a issue about pump placement in the system. I am not big on this system.

    While talking to Holley about a EFI systems for my Jeep. The Tech/salesperson sent me info about a dual tank system they have. The Holley system uses two fuel pumps, one for each tank. When you switch to a tank, you switch to the in line pump that servers that tank.

    Holley EFI 534-37 Dual Tank Fuel Pump Kit.

    On the link, there are install instructions, look at page 2 for wiring diagram, will refer back to this
    The issue with the Holley system they sell, you get the high PSI Pump.

    I am very interested in this system and after some research I came up with this.

    On eBay I found this system.

    POLLAK Universal 6 Port Fuel Gas Dual Tank Selector Valve KIT | eBay

    From what I read the Pollark valve is USA made.

    Amazon has a relay.

    https://www.amazon.com/Pack-EPAuto-...ay&qid=1609807621&sprefix=87a+,aps,219&sr=8-6

    I need input here, the amazon relay link, is that the same one that is in the Holley kit?

    With this system there will be a pump for each tank, the pumps will be close to the tank which the manufactures like. With two pumps, if one goes out, if you can get gas to the other tank you will be good. I plan on using the Holley Mighty Mite pumps, they have a 12 inch lift. I will have two fuel gauges, one for each tank. I plan on putting fuel shut offs at the pumps and may put six shut offs at the valve so it can be isolated if it goes out.

    Will this work?
     
  2. Jan 4, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    The Pollak valve is used on a lot of applications, including Chevys with a factory dual tank. You can also find it in the parts listings at RockAuto. It switches both the fuel feed and return, and the gauge from a single toggle switch.

    I would not use two pumps, but instead put the valve as far back as possible and the pump just after the valve. It should work fine if you keep the pump low compared to the tanks. An alternative is to use a mechanical pump, and leave that in the factory location on the engine. It can easily pull fuel through the valve.

    To me, that looks like the Pollak valve in the Holley kit. I am surprised that it will withstand the 100 psi pressure of that type of EFI fuel pump, but apparently it can. Sellers of the Pollak valve will have instructions that will tell you what pressures the valve will withstand. Since you want to run low pressure pumps, it should be fine. Just follow the instructions from Holley, but use the Pollak valve and the low-pressure pumps. In the Holley instructions, they are using the valve's switching which usually goes to the respective sending units for fuel level. This is described in the Pollak valve instructions.

    More Information for STANDARD MOTOR PRODUCTS FV5K

    The relay is a Bosch type, common as dirt. I buy them from Parts Express. I don't understand why this is an issue. DIscussed in depth here Headlights Relays In Absurd Detail including a bunch of links.
     
    Last edited: Jan 4, 2021
  3. Jan 5, 2021
    garage gnome

    garage gnome ECJ5 welder 2021 Sponsor 2020 Sponsor

    Western MA
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    Some dual tank systems have the bigger tank pump fuel into the smaller tank, no transfer valve needed. That would be very easy to rig up. This is what I plan on doing to Snowshoe when I get to that point.
     
  4. Jan 5, 2021
    dozerjim

    dozerjim Member 2021 Sponsor 2020 Sponsor

    western New York
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    To add to Nates idea a switch with a timer that would pump for say 5 minutes and shut off automaticly so that you dont over fill primary tank from auxillary tank :watch:
     
  5. Jan 5, 2021
    colojeepguy

    colojeepguy Colorado Springs

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  6. Jan 5, 2021
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    A setup I like from a simplicity standpoint is the Ford 89-97 F-series automatic selector valve. There is an electric fuel pump in each tank selected by a switch on the dash. The selector valve automatically switches the return line to whichever tank is currently providing pressure. They are expensive new: https://www.amazon.com/Ford-F1uz9b263b-Reservoir-Assembly-Selector/dp/B0042HFX68, but should be cheap in a wrecking yard.

    Here's a page showing how they work: Ford E
     
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  7. Jan 5, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    A few points -

    The brass 6-way valve is more expensive than the electric valve. It is possible to use two 3-way valves (much less expensive) and switch them both, rather than buy the expensive valve on a single shaft.

    What advantage is there in feeding one tank from the other? Just switch to the full main tank when the aux is empty. Same number of pumps. In a Jeep, it has the added advantage of redundancy - if one fuel pump fails, just siphon gas to the other tank and use the other. I'd also worry about over-filling the main tank, and pushing gas out the filler neck.
     
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  8. Jan 5, 2021
    SoCalNickG

    SoCalNickG Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    My 71 (V6) has the factory rear tank and PO added the under seat tank. It has the stock mechanical fuel pump and a manual three way valve connecting the two tanks delivery lines. When switched to the under seat tank the bypassed gas is returned from the pump to the rear tank via the original plumbing. The fuel gauge (not factory) can be toggled between the two tanks with a dash switch. In practice I run off of the rear tank until there is about 1/2 to 1/3 of the gas left, then I switch the fuel delivery to the side tank while leaving the gauge reading from the rear tank. The fuel pump transfers fuel to the rear tank, while running on the under seat tank. When the gauge shows the rear tank is ¾ full I switch back to the rear tank. Rinse and repeat until under seat tank is empty. The fuel is moved to the rear tank faster than I thought it would. I can't take credit for the system but it is simple and it works well.
     
  9. Jan 5, 2021
    Jw60

    Jw60 WRPD855 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I'm confused are you using the force fuel system or making one to better suit your needs?

    The return for the fuel injection goes to the fuel system and it's reservoir will eliminate any issues with supply while between tanks. All you need is a single 3way valve before a low pressure pump to the force fuel system reservoir and a switch for the guage.
     
  10. Jan 5, 2021
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    The FiTech Force Fuel needs a return line to the gas tank: https://static.summitracing.com/global/images/instructions/fif-50004.pdf

    Realistically, if the original poster is adding electric fuel pumps in or near the tanks and a selector valve (implying plumbing work), I don't see what the $400+ Force Fuel gains them. It's only purpose is using the vehicle's original low-pressure fuel pump/lines to get gas from the tank to the engine compartment. If you're changing the pumps/pllumbing anyway, you might as well put in high pressure pumps and be done with it. Also.... the pump in the Force Fuel pump is a single point of failure negating the advantages of having dual pumps back at the tanks.
     
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  11. Jan 5, 2021
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    A friend got the FiTech Force Fuel for his '69 Ford truck with the intent of re-using the existing lines/mechanical pump for easy bolt-in. ....only to find out he needs to run a return line to the tank. It's an in-cab tank, so it means running adding a fitting to the top of the tank and a fuel line behind the seat. So much for "easy bolt-in". It's stalled his project because he's not super motivated to drain the tank, pull it out, and drill holes in it.
     
  12. Jan 5, 2021
    SFaulken

    SFaulken Active Member 2021 Sponsor 2020 Sponsor

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    Meh, that's not such a big deal. Just wait till you've driven it good and close to empty, and then do the thing. No need to drain it, if it's already running, you just wait a bit longer. They're really quite easy to remove.
     
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  13. Jan 5, 2021
    Steve's 70-5

    Steve's 70-5 Active Member 2020 Sponsor

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    I have a issue with the fuel lines under the Jeep running at 58.5 PSI. It's just me, I prefer low PSI fuel lines.
     
  14. Jan 5, 2021
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I can see that being a valid concern.
     
  15. Jan 5, 2021
    mike starck

    mike starck Member

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    I have a inboard engine in my boat with BOSCH f.i. on a 383 chev.The fuel supply is delivered to the engine by a low pressure electric pump.Then it goes to a high pressure pump that is mounted in the engine bay to operate fuel injection.Works very well.This is a factory setup.mike
     
  16. Jan 5, 2021
    colojeepguy

    colojeepguy Colorado Springs

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    Absolutely true, thats what I had on mine for awhile. I decided to spend the extra $ for the 6 way valve and its much nicer :)
     
  17. Jan 6, 2021
    45es

    45es Member 2021 Sponsor 2020 Sponsor

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    In all reality, why? There are thousands of vehicles on the roads today that run high pressure fuel systems and several carry the name Jeep.

    Something I keep asking myself is, is the OP going to use an electrical pump or the mechanical pump to supply fuel to the FiTech Force Fuel system? Both have been discussed and I am not clear as to what was decided. I don't know anything about this jeep and therefore don't know if anything has been modified or not. If the jeep is stock and multiple electric fuel pumps will be used simultaneously, an upgrade of the original 50 amp alternator is probably wise. FiTech doesn't share any electrical load information about the systems that I found so a person must speculate. Each pump could pull approximately 10 amps. The ECM/fuel injectors could also be about 10 amps. Add in a fan, windshield wipers, lights or any other other electrical device and the fuel injection system will not perform very well.
     
  18. Jan 6, 2021
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    It's not a concern I personally have. I've been driving fuel injected vehicles with no issues for 30 years now. However, I'm not going to argue with someone who doesn't want high pressure fuel lines under their own off-road rig. If they are not comfortable with it, there is no reason for them to do it.
     
  19. Jan 6, 2021
    45es

    45es Member 2021 Sponsor 2020 Sponsor

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    Nor am I going to argue and that wasn't my point. I was just curious what the concern is.
     
  20. Jan 6, 2021
    Steve's 70-5

    Steve's 70-5 Active Member 2020 Sponsor

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    I started this thread to have input on what other people have did with dual tanks. I did a search on the forum and most of the information was in build threads. I started this thread so information would be in one location for future reference.

    At this point I have no idea what I am doing for fuel transfer.

    I have the Force Fuel in the garage , so anything I run will be low pressure. There have been a couple good ideas on what to do, Nate's idea about pumping from one tank to the other has got me thinking. From talking to tech. people and what I have read, manufactures want the pump as close to the tank as possible. Most electric pumps are push, with this, I do not see how one pump will work with dual tanks. Yes it might work.

    I deal with stuff at work that is not done right all the time. I have to fix it, which gets old after a while, but it is my job. Because of this, I read instructions and follow manufactures recommendations. This has a bearing on what I plan to do.

    I have a 12si alternator on my Jeep, mostly a 1970 stock Jeep. The pumps I am looking at, instructions are saying to use a 3 to 5 amp fuse. If I do the two pump system only one pump will run at a time.
     
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