Deep CJ-6: Day Twenty Fuel Tank
Short Cuts

By: Terry L. Howe - 5/2003

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Inside the fuel tank is the sending unit and some baffles. You can see the hose for fuel input and the two lines for to the engine and a return.
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One the bottom of the fuel tank is a skid plate made of 14g diamone plate.
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With the top welded on, there is just a small access hole to get to the fuel pump and the sending unit.

It is hard to find a 20 gallon fuel tank for an early CJ. The frame rails are close together, so you cannot use later gas tanks, you cannot even use the later 15 gallon tanks. The 15 gallon tank that came with my Jeep leaked, so I needed to do something. I decided to make my own tank and my advice to anyone that comes to this same conclusion would be don't do it! The reason I would advise against making your own fuel tank is it is hard to make it leak proof, it is very time consuming, and it is potentially dangerous.

Part of the reason my tank was hard to make leak proof was it was too big to make out of one sheet of sheet metal and my original plan did not work quite right. I had extra seams that wouldn't be necessary on another tank. When I first bent my tank, it turned out too big and didn't provide enough clearance with the leaf springs. I had to cut it down and create a seam where I should of had a bend. I used the "hillbilly" brake to bend the metal. I just clamped a piece of angle iron down where I wanted the bend and pushed the metal by hand. I finished off the bend by hitting it with a rubber mallet.

I tested the tank, by pressurizing it with 20psi of air from my air compressor. This could be potentially dangerous if the tank blows up, but I got lucky. I put soapy water on the tank to find air holes, dried them off, depressurized the tank, and welded them up. It took me nearly all afternoon to find and stop them all up. The welds are ugly, but it seems to hold. There are no leaks that I know of yet.

The other reason I would recommend against making your own tank is it is time consuming. I have this unit as one day, but I have a long 2 days at least in this project, probably closer to 3 days. Part of the reason for that is my original plan had to be modified, but even then, setting up the fuel pump, sending unit, baffles, fill hole, access hole, ... took a lot of time.

The other reason I would recommend against building your own fuel tank is it is potentially dangerous. You need to run wires through the tank. You need at least a sending unit wire and maybe a wire for your fuel pump. If anything goes wrong, your fuel tank may blow up. Comforting thought.

The end result is not pretty, but I think it will be functional. Mathematically, the tank should hold 24 gallons or so. From experience with other aftermarket tanks, I expect to get 22 gallons or less of fuel in it. To calculate the number of gallons of gas I expect the tank to hold, I just divided the volume by 231. An easy number to remember if you are familiar with the 231 Buick V6, the gallon engine. My fuel tank was 25"x15"x16" and with a few gallons taken off for tapered sections of the tank, I got 24 gallons.

I was able to use the extra space provided by a 2" body lift to move the tank up higher and the clearance isn't bad. The tank is built mostly from 14g cold rolled steel and it has a 14g skid plate welded on the bottom. It should take some abuse.