If you can get some elevation on your truck or equipment trailer, a larger portable marine fuel tank works great. I have one on the farm that I have elevated, then just gravity feed down into the mower, tiller, etc.. I just have a length of fuel hose with a QD on the tank, and a ball valve on the end of the fuel hose. To get the initial siphon going from the tank, I just have a cheap rubber primer bulb I temporarily place on the end of the fuel hose to get some flow going, but once it's primed, it will be good unless you break the connection for some reason. Of course, you need to figure out how to keep anyone else from stealing it. The problem with pulling off the vehicle fuel system is that fuel injected engines use a small low volume high pressure fuel pump, so not really good for transferring fuel. Otherwise, they do make some portable fuel tanks with larger capacity like a hand truck with a pump on them, so you could just load it up on your equipment trailer along with the other equipment.