Ideas for dual gas tanks

[markh11]

As I get ready to install my new auxilliary gas tank on my FJ40, I am wondering what are all of my options for delivering fuel to my carberator (new Weber) that have been tried (and actually work )?

I have read (often) where people have switched over to electric fuel pumps (replacing their stock mechanical) and adding a pressure regulator. I have also read almost as many horror stories about the poor reliability (needing to carry a spare fuel pump) and the electrical issues (fire, shorting out, broken wires).

So my question to all of this... Will a stock mechanical fuel pump be able to draw fuel from the rear tank (back of the FJ40 underneath), and with the use of a bypass pressure regulator and a multi-port fuel valve (switches both the fuel delivery as well as the returned fuel to the selected tank), deliver the proper pressure and reliability for continued use?

If not, what options would you recommend, and why (pros and cons would be appreciated)?

 

[Downey]

(a) I don't know if a stock mechanical fuel pump can pump all the way from your rear tank or not, but you are leaving alot of room for vapor lock with the mechanical pump. Vapor lock occurs between tank and pump, consequently if the pump were mounted back by the tank, less exposure!!
(b) Electric pumps are inexpensive, carring a spare won't cost that much, and buys alot of peace of mind.
(c) Mount an electric switching valve mid way between both tanks (a good location would be on or near the rear tubular shock mounting crossmember).
(d) I'd mount an electric pump below the body, mid way between both tanks (just down stream from the electric switching valve). Mount a fuel filter before the pump (between electric switching valve and pump) because electric pumps are sensitive to particles of poo-poo. Now fuel can easily gravity feel the short distance from tank to switching valve to filter to pump, then pump can easily push fuel up to the engine (electric fuel pumps are pushers, not suckers).
(e) Now get a double pull/double throw (DPDT) switch that will switch from tank to tank AND sending unit to sending unit simultaneously. If you don't know how to wire this, send me your mailing address and I'll send you a copy of our tank installation instructions that shows all plumbing and wiring choices!!!

 

[Living in the Past]

I bought my 68 back in 1974 with a spare tank. The manual switch over valve for the two tanks is located just inside the driver's door next to under seat tool box. The mechancial fuel pump has never been a problem. It could even prime all the way from the back tank to the carb. Running the stock carb now but over the years I've run many carbs including a Holley 500. Used a Downey adapter. Back in 74 I think the 500 was the recomended holley before the 350 took it place. That was a long time ago. Never any problem with vapor lock here in Arizona either. Probably helps the exhaust is on the driver's side and the fuel lines on the passenger's side.

 

[3_puppies]

my only thought about Jim's advice above is the stock pump will be fine with the extra tank. FJ55's are much longer than a 40 and the stock pump works just fine, same with the old FJ45LV. just my opinion.

 

[Fuzzy Logic]

Vapor lock occurs between tank and pump,

More like between the pump and carb. Heat from the engine, don't you know.

 

[craptabulous]

More like between the pump and carb. Heat from the engine, don't you know.

or exhaust under the vehicle if its mounted closely to the lines .

 

[Combat Chuck]

My own plan for a reserve tank is to have a cheap electric pump act as a transfer pump, and move the reserve fuel into the main tank, thereby eliminating the risk of the actual tank-to-engine pump losing its prime. whatever floats your boat, really, when it comes to fuel pumps, it's always best to have a spare.

 

[psreno]

FWIW, I've run two tanks on my FJ45 (almost as long as FJ55) with just stock pump on the SBC. I don't think there's much difference between the diaphragm pumps in terms of capability.

Then I also have el cheapo low pressure electric pump (and switch) for a spare to the mechanical, or if I need to xfer fuel to another vehicle.

 

[rusty_tlc]

I ran a Confer tank for many years. All I used was a solenoid valve to select which tank I would route to the stock fuel pump. I never had any issues.

 

[Toshi38]

when I got my 40 it had the rear tank... and it had the stock pump and an electric thing to select the tank. Return lines only went to the stock tank though. Worked fine just had to watch you didn't overfill the stock tank. Now I have my return line plugged and only run off the rear tank.

 

[bsevans]

I use the stock mechanical fuel pump for my two tanks and have never had a problem. I have a supply and return line on both tanks and use a Pollak fuel tank switching valve that switches the supply, return and fuel gauge sending unit. The really nice aspect of this valve is that it is only powered to switch tanks and then shuts off until you flip the switch to use the other tank.

light truck 6 port motor driven valve
You can see where I mounted it and the control switch in the following photos.

 

[BC40]

I've run a rear tank with an electric switch valve for years. No problem using the stock mech fuel pump feeding the weber, but I don't have a return line in my setup.

 

[markh11]

I use the stock mechanical fuel pump for my two tanks and have never had a problem. I have a supply and return line on both tanks and use a Pollak fuel tank switching valve that switches the supply, return and fuel gauge sending unit. The really nice aspect of this valve is that it is only powered to switch tanks and then shuts off until you flip the switch to use the other tank.

light truck 6 port motor driven valve
You can see where I mounted it and the control switch in the following photos.

This is exactly what I was considering! How did you mount the 6 way electric valve?

 

[bsevans]

This is exactly what I was considering! How did you mount the 6 way electric valve?

I took a piece of Aluminum plate (1/4") and cut it to mount the valve and also pick up three existing threaded holes in the frame. I do not currently have a photo of the installation or the plate. The front two mounting locations are used to mount a protective cover for the brake line (I think). One thing you have to do with this setup is have a fuel filter on each tank before the valve. I used large housing racing filters with 8 micron elements. The first photo is the filter for the front tank. The filter for the factory tank also mounts to the Al plate that the valve is mounted to. If you want more info then refer to my ROTW-My Yoda in my signature. See posts 33-36. The switch used to change from tank to tank is not a normal switch. You need to use the Pollak switch for the valve to properly operate.

 

[numby]

I've used an electric pollak switch for 20+ years with dual tanks on a fullsize pickup with a mechanical pump. No issues ever. I finally bought a back-up from Northwest Metal Products - Since 1977 because, well, the switch is getting kinda old. Not as old as all the switches in my Cruiser though