My auxiliary fuel system is a good example of the thought process I used when modifying my truck. Since fuel would frequently be scarce on my travels, I wanted to increase the fuel capacity of my truck and extend its driving range. After researching companies that build and install auxiliary fuel system, I couldn't find anyone who made an auxiliary tank for a short bed, quad cab Dodge that could be located behind the rear axle.
I worked with Safari Vehicles to design and install a system that made no modifications to the factory system, and also gave me a redundant fuel transfer pump. Safari Vehicles installed an 18 gallon marine fuel tank in the factory spare tire location, and I added an additional factory transfer pump to transfer fuel from the auxiliary tank to the factory tank.
When the main tank gets low, I simply flip a switch on the dash to transfer fuel to the main tank. If a leak ever develops in my auxiliary tank, I can simply use the factory fuel system. If the factory system ever develops a leak, it would be a relatively simple task to plumb the auxiliary tank as my main tank and eliminate the factory tank until repairs can be made. If my factory transfer pump ever fails, I can just swap it with my auxiliary tank pump.
My camper heater and stove draw diesel fuel from the auxiliary tank, so I won't ever run my main tank dry by using the furnace or stove. This system achieves my objective of increasing my driving range, it is simple in design, it doesn't adversely impact the factory fuel system, and it also provides me with a redundant fuel system.
This system has been working well, except that my fuel fillers are located too low, so filling the tanks is difficult and they must be filled very slowly. I will be relocating the fillers to a location about 2 feet higher on the side of the camper that will resolve this problem.
This is my second attempt at an auxiliary fuel tank system. The first attempt was a total failure because the company that plumbed it was clueless. They ruined my first tank when they cut an oblong hole in the top of the tank for a vent hose. They then used hose that was incompatible with diesel fuel. When I tried to fill the tank, fuel ran straight onto the ground. After spending a couple of days with them trying to figure it out, I gave up. All of their plumbing and the botched tank had to be replaced.