Upgrading the OEM fuel system was an easy call - the original fuel tank on the CJ-2A was a 9 gallon tank located under the driver's seat. That would give me less than 150 miles per tank, which wouldn't work for my intended use. So I did some online research and decided on a polyethylene replacement tank from MTS. MTS tanks are made from a high-density, cross-linked polyethylene with 1/4" wall thickness for strength. There are no welds or seams to fail or leak, and rust will (obviously) never be a concern. The tanks are made to withstand extreme temperatures without cracking, and they come with a five year warranty.
The tank I selected has a 21 gallon capacity and installs in the traditional CJ-5 location behind the rear axle. Although designed for the '72 and later CJ-5, this tank will fit the 1970 frame with a later model skidplate and extensions. I installed the in-tank sending unit prior to test fitting the tank, and I clocked the fuel lines toward the passenger side frame rail where they will be routed to the carburetor. After test fitting, I found that I needed to trim some material from the triangulated rear frame braces in order for the tank to snug up tightly into the frame. With the skidplate extensions installed on the crossmembers at the front and rear of the tank, the skidplate bolted up perfectly. Flipping the bare frame upside down made installation much easier due to free access to the bolts.
With this tank setup, my range should be extended to 300 miles per tank, which is a huge improvement over the stock system.
As with nearly everything on this project, I had to get creative with the fuel filler configuration. The main filler and vent hose ports exited at the passenger side rear of the tank, so the optimal mounting location for the filler would be on the passenger rear quarter panel behind the wheelwell. I selected a fuel filler mount and filler neck for a later model CJ. I then chose what I determined to be the best location to align with the tank ports, and marked the body for cutting. To cut out the mounting hole, I used a Craftsman electric oscillating cutting tool which provided a quick cut with clean edges. For the initial cut, I intentionally went a little "small" and then cut away additional material while test fitting the plastic filler mount. Once I achieved a snug fit, I marked and drilled the mounting holes.
Next, I moved on to mounting the filler neck into the plastic mount. I clocked the filler neck so it pointed toward the tank ports and lined up the mounting holes in the filler and plastic mount. For aesthetics and corrosion prevention, I used stainless steel button head bolts to attach the filler neck to the mount and the mount to the body.
On to the next challenge: I needed to find a hose arrangement to fit the 2 1/4" filler port on the tank, the 1" diameter filler neck on the opposite end, and that would be flexible enough and short enough work within the available space. This one had me a little worried until I found FillerNeckSupply.com. This website specializes in one thing and one thing only, and they had all the components I needed to piece together my solution.
Not knowing exactly what I would need, I ordered a rubber reduction hose, sections of filler and vent hose, hose clamps, and various metal and rubber adapters to ensure I would have what I needed. (The vent hose was no problem as the vent port on the tank and the vent hose diameter at the filler neck were the same size.) The really trick components that saved the day were four rubber reducers that fit snugly within each other and allowed me to address the drastic difference in hose diameters. As you can see in the pictures below, the combination of components came together to form a solid solution.
For getting the fuel from the tank to the carburetor, I purchased two 12' sections of hard fuel line and a length of rubber fuel hose. I selected a standard inline fuel filter, which I mounted between the fuel pump and the carb. The OEM mechanical fuel pump would work fine for my needs, and I had already installed a new mechanical pump during the engine build. Yes, I considered swapping from a carbureted system to fuel injection, but to keep costs down I decided to stick with the OEM system for now. That may change in the future.
Since the rear brake line and wiring harness already occupied the driver side frame rail, I decided to route the fuel lines along the passenger side frame rail. As I did with the brake lines, I used small clamps with rubber inserts bolted to the frame to secure the lines to the inner frame rail. I took special care to note any locations where the hard lines might contact metal during movement, and sleeved the lines in split rubber hose. This should prevent damage to the fuel lines while jostling around off road.