Adding a Series Gas Tank

by Jeff Berry

Two hundred miles to a tank just didnít cut it for me so I started researching ways to extend the range of my D90.  I found the addition of an auxiliary tank under the passenger seat the most viable option.
The idea here was not to try and duplicate the entire fuel system.   The high pressure pumps cost a fortune, and cost was a primary concern.  I created a transfer system similiar to the way aircrafts transfer fuel. Just run the main tank down to below 1/4 and then flip the dash switch, activate the fuel pump and transfer the fuel from the auxiliary under the seat to the main tank.  I checked out  the variety of tanks to choose from and made the most cost effecive decision.
1)  Go with a Euro D90 tank.  (their Defender tanks are factory installed under the passenger seat) 
 I faxed and got prices from various Euro companies.  They make two types of systems:  Internal fuel pump tank (very expensive)  and external fuel pump tank. Part # s are here.  Most of the prices were very good but the problem is shipping. So I opted to find something locally.
2)  Go with an after market aux tank. (Brit Pac has one you can install, you fill it by lifting the seat like the Series I) 
Brit Pacs aux tank specifically designed for the NAS D90 was good but it seemed awfully expensive (I donít remember the price) and I wanted something easier to use. ( The Series I methodology of filling was not appealing) This option is good if you do not like the idea of cutting a hole in the side of your Rover for a filler neck.
3)  Get a Series II-III tank and alter as necessary to fit as a D90 saddle tank. 
4)  Fabricate your own tank. -possible if I knew how to weld :(
So I decided  to go with a Series II-III set up. It was the best bang for my budget (less than $400), and I thought it was the safest with the added protection of an outrigger. The following is how I did it:
1)  Find and order your parts,  I got the stock Series tank from Brit Pac, it was an aftermarket, only one seam and an extra plate welded on the bottom for protection.  Euro Parts gave me the outriger and various hoses and gaskets. The hard to find parts:   The stock 88" fuel filler tube assembly is no longer available, and neither is the galvanized body piece that holds the filler tube and gas cap.  I went with a yard (Bit of Brittian in NY) and got the fuel filler, galvanized body piece, fuel lift pipe, and fuel sending unit.  This saved me a lot of cash.  
2)  First, I drilled out the spot welds and rivets that hold in the tool box that's mounted down there now.  I also relocated the fuel filter for easier access once the tank was installed.  If you have a 95, you have to relocate your ECU unit as well. After removing the box  I primed and coated the whole underside with Noise Killer Blue, a sound deadening product used for stereo setups.  Then I undercoated with a spray on undercoating. 
3)  I installed a rocker switch on the console and ran a wire where the new fuel pump will be mounted. I put mine on the frame near the wheel well.  Run your fuel line BACK to the main tank, use a tee fitting to attach it to the vent line on the filler neck. I also installed a toggle switch wired to the fuel gauge (green and black wire) then ran the wire to the where the new tank will be mounted.  This way I will be able to tell how much fuel is in each tank by just toggling.  Thatís about all the wiring. 
4)  Next, the tank and all my parts  came in the mail, so I went out to see how the Series tank would fit where the tool box used to be.  Not very well, it seems the front radius arm mounting is in the way.  Nevertheless, through some Ďpersuasioní on my part I got it to slide up to where the neck of the tank hit the floor of the Rover just behind the seat.  I marked the spot then cut a 3x6" hole in the floor so the filler neck came up inside behind the pax seat.  If you Ďpersuade a tankí make sure before the tank is permanently installed to check for leaks with air pressure. In retrospect, I should of gone with the Euro D90 tank.  It would of cost a bit more but the installation would of a lot easier. 
5)  The front outrigger was modified slightly so the tank would sit a little higher, giving me a inch or so more clearance below for rock climbing.  I chose to bolt on the outrigger as opposed to welding. I drilled two additional  holes in the frame and used an existing transmission mount. Bolts made it easier to fit the alien tank in place.. I fabricated an L bracket so the rear of the tank could mount to the existing brackets welded to the factory outrigger.  
6)  In order to fill the tank from the outside a hole had to be cut for the filler neck assembly.   yikes!!  I made a pattern then rechecked, realigned and rechecked and.. then made the cut. The galvanized filler plate, filler neck and cap  was etched, primed and painted Alpine White. The seat belt reel needed to be pivoted (cut and re-welded, primed and painted) 90 degrees so it did not interfere with filler neck assembly.  Now the filler plate could be riveted in the newly cut hole.  The filler neck was screwed to the filler plate.
7)   I fabricated an aluminium cover  and riveted the plate over that 3x6 hole I made in the floor for the tank neck and vent.  Now,  the and the fuel vent and fuel hose could be clamped in place. The gas cap needs to be breathable, if not, a one way check valve needs to be installed in the somewhere to equalize the pressure in the tank as the fuel is transferred out.
The finished product looks pretty good.  Itís aesthetically pleasing to the eye, the passenger seat lost a few inches in recline, but the extra 175 miles I get to a fill up offsets that.  Besides it was fun to do, a learning experience and made my D90 a bit more unique.