Mr. James Wesley; Rawles:
I keep a lot of extra gas in five gallon jerry-cans around my new farm/retreat wanna-be, for emergencies. (Stabilized with PRI-G , of course.) Yeah, I know that siphoning–especially if you prime it “by mouth”–is not safe. (Gag!) To make it easier and safer to transfer gasoline into or out of vehicle gas tanks, is there any transfer device that I can use use? Perhaps something that would plug into my pickup truck’s cigarette lighter [12 volt DC power] jack? What can I buy that is cheap off-the-shelf, or cheap to cobble together myself? Oh, and its also gotta be safe–I don’t want to accidentally create a fuel-air explosion. <VBG.> TIA , – Lt. Dan
JWR Replies: Every well-equipped retreat should have at least one “field expedient” 12 VDC  fuel transfer pump. These pump rigs are popular with dirt bike, ATV , and snowmobile enthusiasts. They are very simple to construct. Here are the materials that you will need:
1 – Automobile or truck electric fuel pump. (The least expensive pumps come from automobile wrecking yards.)
2 – 15 foot lengths of heavy rubber hose–approved for use as fuel line–of the proper diameter for the fittings on the fuel pump.
2 – Stainless steel fuel line clamps. (Such as “Aero-Seal” brand, or similar , that are tightened with a screwdriver.)
15 to 20 ft. – 16 AWG  (or heavier) gauge insulated two conductor wire. (This will be the power cord for the pump.)
1 – “Cigarette Lighter” type male plug , available from any Radio Shack store. (Again, for the power cord for the pump.)
1 – Roll of black plastic electrician’s tape or better yet, some thermoplastic “heat shrink” tubing .
1 – Scrap of 3/8″ thick (or greater thickness) plywood, measuring roughly 16″ x 16″. (To mount the fuel pump.)
The construction method should be self-evident, based on the materials listed above. If you’d like, you can add an electrical switch to the power cord for convenience, but make sure that you get a high amperage switch that is rated for DC, and that you position the switch within a couple of feet of the dashboard plug so that the switch is inside the cab of your vehicle. That way there is far less chance of generating a spark inside of a gas vapor cloud.
If your vehicle uses an electric fuel pump, then I suggest that you use an identical pump to that used in your vehicle as the basis for your transfer pump project. That way you will have spares on hand, in the event that your vehicle’s fuel pump or any portions of your fuel system’s flexible fuel lines ever fail.
OBTW, you can also add and “in line” fuel filter to your fuel transfer pump rig. Again, it is best to use a filter cartridge that is identical to that used in your vehicle. (Always think in terms of: “Spares and redundancy, spares and redundancy.”)
One other optional nicety is a one foot square scrap of plywood, to bolt the pump onto. This will keep the transfer pump out of the mud or snow. It also provides a handy place to mount some large hooks, so that you will have a neat way to coil up the power cord and the fuel transfer hoses, for storage. A 15 foot length of hose should be able to reach any vehicle fuel tank, or even down into an underground tank.
There are commercially made equivalents to this fuel pump rig, but they cost more, and they won’t provide you with a spare compatible fuel pump–for the event that your vehicle’s original pump goes Tango Uniform.
1.) All of the usual common sense precautions for handing gasoline and gas cans apply: Use only DOT -approved fuel containers, No sparks, No open flames, Don’t turn on any radio transmitters, Beware of static electricity build up, et cetera. See this Oregon State University web page for details on fuel handing safety. 
2.) Some later model vehicles have “anti-siphoning” filler necks on their gas tanks. Check for this before you head for the boonies with an ATV trailer.
3.) Cover any exposed electrical connections with tape or heat shrink tubing, to avoid sparks or shorting.
4.) Keep one eye on your vehicle’s gas gauge and your other eye on the can that you are filling (or pumping from). It is not just an expensive waste to spill gas on the ground. It is also toxic and a fire hazard!
By coincidence, soon after I wrote the first draft of my reply, I got an e-mail forwarded by Alfie Omega, a regular over at the outstanding Alpha Rubicon web site.  There, “Pike” has plans for building a very similar fuel transfer pump rig. (I guess that he had seen the same type that I had seen.) A couple of nice touches with his with his design that mine lacked are that the mounting board has a carrying handle cut into it, and there are hooks mounted all the way around the perimeter of the board, for hose and power cord stowage. But a couple of detractors are that his photos show and on-off switch mounted to the board (which as previously mentioned could put it in proximity to gas vapors), and I saw some exposed wiring terminals. If those terminals were touched by a metal object could cause a spark.