Shortly after buying our Gen 3 SWB 2 years ago, I was very dis-appointed to find that no one offers an aux fuel tank. About 3 months ago, SWAMBO out of the blue suggested we go to Mabuasehube in the first week of January. We have never done a trip like it before and I calculated we needed 3 jerries on the roof of diesel, 4 to be safe. Used a consumption of 5km/l to be super conservative. I was reluctant to put any more weight on the roof which meant the back of the swb was not enough space for everything to be self-sufficient for the trip.
I found myself thinking about doing a custom fuel tank for the shortie. I went in to an exhaust shop, deleted the back silencer (My back silencer was not a free flow box), and got them to reroute the exhaust straight out and to the left side of the vehicle. Sound of the car didn’t change too much. It is a deeper sound that you only really hear on start up, idle and heavy acceleration. (We are game viewers, so I actually didn’t want it to be louder, so I was happy that it was only a slight change.) I wrapped the exhaust with some kind of strap that I was told was a heat shield as the exhaust pipe will sit close to aux tank. I then took a deep breath and took a grinder to the storage unit underneath the boot. SWAMBO and I decided that it was useless, on a trip, you can’t get to it without unpacking a full car and during normal use, you can just chuck everything in the back.
So back storage unit came out. This creates a very large space for a tank. I got a stainless steel plate profiled to cover hole. Using the existing screw holes and created a few more holes with rev nuts in them. Then placed some of the adhesive foam to seal out the water and dust. I draw up the design for a tank. Front of tank was level with rear diff and sloped up so that it stayed level with tow hitch and recovery points, basically it matched the lowest point under the car. Capacity was sitting at about 100 litres. I then decided, rather safe than sorry. So I lifted the bottom of the tank so that it sat 3 cm above the diff and tow hitch and reduced its width and height to ensure I had ample space all around the tank. Final tank is around 83 litres according to the cad model. I built a mock-up of the tank using electrical conduit pipe and tested space underneath the car.
Drilled 4x holes through the cross member for an M10 Bolt. Created two clamps that clamp onto the square tube of the tow hitch. Designed a “cradle” that bolted onto the two square clamps and then onto the 4x holes through the cross member. This cradle holds the weight of the tank only. I did another strap that goes over the top of the tank and bolts onto nuts that are welded on the underside of the chassis. Top strap stops tank from bouncing up on corrugated roads.
Drilled a hole through the right hand side of the chassis for a breather pipe of the tank.
Now to the tank itself, the lowest point of the tank sits behind the rear diff so it can’t gravity feed the main tank. Needs a pump. I drilled two holes underneath the cross member and put two rev nuts and mounted a Huco 443010 Suction Pump. The fuel is sucked up from a pipe that is bolted on from the top of the tank. (After reading some issues on the forum of fuel not being sucked after a dent in the tank, I wanted a removeable pickup). Fuel is sucked through a filter and is then sent to the main tank. I took the vehicle to Gerbers 4x4 and they were happy to remove the filler neck and weld in a splitter, another breather port and a new inlet for the fuel coming from the aux tank.
There is also another hole for a fuel float in the tank so that I can see how much is left in the aux tank. Initial idea was to get a fuel float off a wreck, modify it to account for the new depth of tank and connect it to the existing gauge in the dash via a switch. I wanted a switch that when depressed, it showed the level in the aux tank, then when released, it shows main tank again. I wanted this function specifically so that I would never forget it on the aux tank and run the main tank dry. I found a suitable switch, but I also found out that the gauge doesn’t continuously read the level, it would read the level every minute or so (I assume it does this so that the needle doesn’t bounce around as the fuel sloshes about. To get the gauge to show the aux tank, I had to hold the switch for a minute. This was not convenient. So I went to midas and got a fuel sender and coupled gauge. I now have two gauges up front. In hindsight, this setup is better as I can monitor and see if there is an issue of leaking. The aux gauge is linked to ignition and it has a light that comes on when the Paj lights are on. I split the ignition line going to the seat warmer switch and the lights from the fog lamp switch.
The tank has a single breather at the top and fills from the standard filling port of the car. The tank is made from 1.6mm Stainless Steel 316L. I had all plates profiles and CNC bent for accuracy. All welding was TIG welded for strength and to prevent plates from warping. The straps were made from 3mm 316L. Baffle plates were included for strength and to stop fuel from slopping about in the turns and affecting handling as all the weight is behind rear axle.
Drilled a hole through the floor at the rear for power cables for the pump and signal for the fuel float. The relay and fuse for the pump sits inside the access panel at the back right of the car. There is no info on the current draw of the huco pump so just put a 4 amp blade fuse. Relay signal comes from ignition line with a switch in the cab. Can transfer from aux tank on the fly. But for last couple of litres, better to stop and listen for change in pump sound when it starts running dry.
A quick comment on my choice of pump. Due to the layout , the pump is mounted higher than the tank. The more popular choice for this application is the facet cube pumps, according to their specs, they have a “wet lift” of 12 inches (which is roughly 305mm). My tank is 350mm deep. Although the sales person I spoke to from the states says it will be fine, I also wanted a fuel filter before the pump. So I was concerned of putting the pump under too much strain. The other downfall of the facet cube pumps is that the models available in south Africa don’t have non-return valves. So if I only empty half the aux tank and turn off the pump, the fuel will flow back down. Next time I put it on, it needs to suck the air up before it starts pumping fuel again. The huco 443010 has non-return valves and the suction is more than enough to lift the fuel. Transfer is slow, about 2 liters/min, so it takes between 25 – 35 mins to full main tank depending on how empty it was.
Before our trip to Mabue, we were in Drakensberg. Filled both tanks and no issues. Unfortunately, 2 days before our trip, we got the dreaded blinking transmission light. (got it occasionally when switching, but always cleared on ignition off so I was not too concerned, just thought slightly sticky switches.) I am not knowledgeable enough to trouble shoot the issue so had to leave vehicle behind and was lucky enough to use my father’s vehicle for our trip. Turns out it was an issue on the selector.
Long story short, it is possible to get a sufficiently big aux tank in the SWB if you are ok with taking a grinder to it. Our 3.2 DID shorty now has 150 litres without jerry cans and over 1000km Range depending on road and what we put on the roof/tow.
Admittedly, it was quite expensive. Total cost was around R10.5k. I also ended up blowing a fuel float due to carelessness, buying much more nuts and bolts than required. Having threaded stainless steel hose nipples instead of just pipes extending out. I also got a much better material. 316L Stainless is very corrosive resistant, I prefer it to the 3CR12 that is used for standard commercial 4x4 aux tanks which is then coated. To me, a coating is something that can come off at some point and cause issues. My tank is also thicker material than normal commercial aux tank. I am confident that most kicked up stones won’t leave dents. The welding I specified is stronger if done properly and therefore requires specialised training. I also now have the ability to brag that we have a one of a kind car and I did it all myself (with the exception of the laser profiling, bending and welding of course.)
Rough Break down of cost
Manufacture of tank plus all straps, brackets and cover plate: +- R7000
Creating new exhaust pipe: R500
Labour at Gerbers: R+-1100
Fuel Pump: +-R800
Fuel Pipe: +-R200
Heat Wrap for Exhaust: +-R200
Consumerables & Nuts and Bolts: +-R500
