AUXILIARY FUEL TANKS?

[Strider]

Howdy,
Been thinking it would be nice to extend the range on my 2008 Toyota FJ Cruiser. I looked at auxiliary fuel tanks and they are just way too expensive: $1500 for an extra fuel tank is just too steep a price.

So I was thinking of a custom, homemade tank. The idea is not to tie it in to the oem tank, but to keep it separate and refill via a pump and hose to the oem fuel fill up point-like a permanently mounted big jerry can.

Looking under the FJ there is a good amount of space that could accommodate an auxiliary fuel tank or tanks, especially in the back behind the bumper. So here are some ideas I had. I am just brainstorming so feel free to express your agreement, concern, or utter horror-lots of people here with great knowledge.

1. Welding up my own tank to fit underneath in the rear. I would use 12 or 14 gauge steel with a skidplate. I own a wire welder that can use gas, so that is one thing in my favor.

2. Using steel tubing (or plastic if there is some made to withstand fuel), capping it off, and mounting it underneath. 1/8 wall steel tubing is pretty good armor and can fit in tight spots, but I think even thinner wall would be fine especially if I can mount it high up.

Of course, this may not be worth the effort (or danger?) and best to stick with extra jerry cans.

 

[Kiomon]

We made some custom tanks for our Unimog camper. The real trick is keeping them from warping. Depending on the size be sure you put in some baffles. All in we made 4 tanks and even with a very skilled aerospace welder, we got some warpage. So just keep that in mind. But if you make a square or rectangular tank, it's pretty easy to put in a sender for it if you want to monitor it.

Big tubing or pipe capped off is simpler and strong, but baffling gets tough. The upside is that you can bend the tubing and get more volume into tricky spaces.

As far as interconnecting the two tanks, I would strong suggest you just tie into the vent line of your stock tank and use a transfer pump. This does mean you would need a separate fill for the aux tank, but it also keeps your two systems independent. So if you got a leak in your homemade tank you could valve it off from the main. I have a little switch on the dash that has a cover on it, so I can flip up the cover and activate the transfer when I need to and it works fine even while driving.

The last big thing to think about is venting on the tank. Be sure you have a decent size vent on your tank. Modern gas pumps can move a lot of liquid and that air has to escape the tank while the fuel goes in. The second issue is that the fuel will off gas. So you need to have a vent for when the camp is on, so that air can still go in and out of the tank. On my Syncro build we had to do some tweaking on the aux tank to get th venting right.

 

[quickfarms]

The tank itself is the easy part. Measure the space and see if a marine tank will fit.

The problem is going to be connecting into the existing fuel system without upsetting the computer in your vehicle. On modern vehicles even leaving the gas cap off will through error codes.

 

[anickode]

The "I own a wire welder that can use gas" part is what makes me nervous. To me, this indicates a generally inexperienced hobbyist. No offense to you intended, but I don't want to be driving behind somebody with a gas tank that was built by an amateur welder slung under their truck. Even a slight defect in a weld will make it seep fuel, which is dangerous to you, your rig, your house if you park in a garage, etc. You need to KNOW it's going to hold fuel before you fill it because once you've put fuel in it and find a leak, you're more or less screwed because it is incredibly dangerous to weld on (even an empty) fuel tank that has contained fuel. Dye penetrant testing is by and far the safest and most cost effective method to accomplish that without sacrificing accuracy, but requires extensive cleaning of the inside of the tank afterwards.

If it were me, I'd TIG it.

My recommendation to you is have it done by a pro. Build a cardboard mockup and have someone else build it.. Unless I'm reading you wrong, and you yourself are in fact a skilled welder who simply lacks a shop full of equipment.

My $.02

 

[kmlacroix]

Also, homemade tanks are not DOT compliant. You may be better off looking for a real, DOT compliant, fuel tank you can mount.

 

[HenryJ]

Is there a chance that a factory replacement tank might work for you? On my S-10 I did as Scott did and added an Isuzu tank: Auxillary fuel tank part deux on my Avalanche I used an F150 tank: BLT Offroad Avalanche

Between marine tanks and OEM replacements, there are lots to choose from.

 

[BPD53]

I had ATI build me a tank for the bed of my Chevy Colorado. I use it as a holding tank that pumps into the factory tank filler neck. The idea and execution was actually pretty easy, but I have almost $700.00 in the setup. I installed a secondary fuel gauge so I don't run the pump dry. I highly recommend ATI. If you give them the specs they will build you a tank. They also have DOT certs for gasoline transfer tanks. I have had good results with my setup, but it is in the bed under a topper. You will need alot of measurements for a filler neck, vent, supply, return and mounting tabs/straps. Good Luck. I love being able to fill up while driving. I would think that anything less than 10 extra gallons would warrant jerry cans, just for ease and price.

 

[Strider]

Good point about the welding/warping/leakage. I am an amateur welder so I see the concerns regarding weld integrity and safety in such a build.
Anybody installed a marine tank or other vehicle oem tank under an FJC? I see there is lots of space underneath but there is also a good sized square contraption right in the middle. Wonder if that can be relocated.

 

[Strider]

So if I weld a tank from steel-lets say 14g-then test it for leaks with air pressure and soapy water, and coat it with sealer... shouldn't that be ok?
I would add baffles ans some ribbing to re-enforce it.

 

[tacr2man]

i would second the usage of a suitable size/shape tank from another vehicle . the variety is enormous , you dont need a guage on the aux tank , just fill it , then you know what you have , you then run the main tank down to a point that you know has enough space for all the contents of the aux tank . If you use a pump say facet cube type , and direct mount it to body or chassis you will hear it pumping , and hear it rev up when the tank is empty , also running it dry for a short time wont hurt it unlike vane types. KISS HTSH

ps dont mount tanks of any type inside the passenger area particularly if gasoline .

 

[peneumbra]

It is technically illegal to mount a non-DOT fuel tank on a highway vehicle. Well, big deal, right?

Unfortunately, such undertakings have resulted in huge fines, should a nosy highway patrol person inquire about your tank. And they are doing so more frequently these days...

 

[red EOD veteran]

Check out a fuel cell. Premade fuel tank that is a reasonable price, and meets the safety requirements. Places like summit racing and jegs have them.

 

[Strider]

Sounds like good advice. I will measure the space down there to select a tank. I hear FJCs in OZ run auxiliary tanks-maybe I can find one of those.
Anyone done this on an FJC?
Anyone know about relocating the charcoal box?

 

[PIC4GOD]

Have you tried the Blue Room http://www.fjcruiserforums.com/forums/ ? There are quite a few people who have either installed a Man-A-Fe tank or developed their own. I think this forum is a little too broad for the speciality stuff you are asking for the FJ. Try some searches in the Blue Room and you'll see some great options. I personally didn't need that much fuel and went with 2 Rotopax holding 4 gallons each mounted on a ChiTown 4x4 rack that attaches to the spare tire holder on the back of the FJ. Let me know you want to see pictures. Good luck with whatever direction you choose!

 

[Strider]

I will try that forum. Thanks!

Pictures would be great.