Fitting a TD5 Auxiliary fuel tank into a TDI 90 (PART 1)

Right, This is my 1st attempt at a guide aimed to help you fit a 2nd fuel tank between the chassis rails at the back of an earlier (pre TD5) 90.

If you cannot use a grinder, weld or get someone to fabricate parts its a non-starter, so dont bother reading on. Also note this is almost a completely fabricated system, nothing is set in stone or exact, you WILL have to use your own ingenuity (power of creative imagination) to make the system work and work well. This guide applies to my 300TDI, earlier models may vary so you may need different exhaust parts and the brackets will likely be different. Also note that I bought this all off another forum member (lucky me) so did not have to make/source the brackets, filler or anything else. It was all (almost) to hand.

A basic run down of the steps:

1. Move Exhaust
2. 2. Cut Rear Cross Member
3. 3. Fabricate Brackets &/or Filler
4. 4. Fit Tank/Cradle/Guard
5. 5. Plumb in Transfer Pump
6. 6. Wire up Switch/Gauge/Sender

Part 1 will deal with steps 1-4 with Part 2 taking care of 5-6

Firstly the TD5 tank sits right were a 300TDI rear silencer is, so the 1st step is to move the Exhaust. I went for a side exit custom fabrication but you can use later TD5 parts. According to other sources, these are:

ESR4526 (silencer)
ESR4527 (tailpipe)

2nd step is to cut the triangular fillet out of the rear cross member. The TD5 cross members have a flat face allowing the tank to recess up flush against it. Earlier ones are not like this. Photo's 1-3 show you where you need to cut and photo 4 shows the section cut out. I had to cut it into 4 sections in the end and do lots of hammering with a chisel to get the thing out. Its not pretty, but it works. Photo 5 shows it primered with my recovery ring (ooo errrr) re attached. Note. If you have a towing assembly or similar this may not work, or you may need to upgrade to a TD5 tow pack. This may also cause problems with not having the right mounts.

So now your vehicle is ready to accept the tank The 3rd step and probably the most time consuming is getting the brackets fabricated. The brackets I have are made to be fixed to the anti roll bar mounts on the chassis rail, again earlier models may vary. You will need to find a way of attaching (or welding) on brackets in this area to hold the Tank. This is where each vehicle will vary throughout the range. Photo 6 shows the brackets a Y piece filler. The filler has been made from a standard filler and a TD5 filler. The reason being the breather pipes are the correct diameter. On the otherside of the standard filler piece is a small diameter pipe which is angled at 90 degree's down the filler. This is how the fuel is transfered from 1 tank to the other.

There are varying options and opinions here in that you could opt for a simple 12v fuel transfer pump system (which is what i have installed) or go for a valve change over system such as a pollak valve which are a little more complicated to set-up and will need the original system interfered with. Also instead of fabricating a Y piece filler, you could cut the bodywork at the rear and install a seperate filler (like a TD5 90). There are many options and it is worth thinking about.

Step 4, The fuel tank arrangments. firstly you need to source a TD5 90 tank (WHK10040). they come up on ebay alot but make sure its for a 90 all the others will not fit secondly the cradle (WFI100070) thirdly the sender unit (WQB100430) then the sealing ring, adapter, and metal ring for fitting this sender in the tank (ESR 3806/ ESR 3807/ ESR 3808). Lastly its worth investing in a fuel tank guard from the likes of simmonites, rebel, paddocks etc. Offer this up and it should all fit snugly underneath, you will also have to remove the towing/lashing rings from the chassis because they will interfere with the installation. Prior to installing the unit make sure all your pipework is secure and that your sender unit is working. Also note the return on the sender will need to be blocked off IF you are using a fuel transfer system. Photos 7-10 show the tank install arrangement.

Right thats Part 1 over. Now go make a cup of tea before reading part 2 :blabla:

G

If you have not read part 1 I suggest you back up and read that 1st (it makes more sense that way)

Part 2 will deal with the plumbing of the 12v fuel transfer pump, filler assembly etc and wiring in the sender unit to a seperate gauge.

So your tank is installed with the sender working properly (you did check it on the gauge 1st right?) with your breather pipes fixed correctly and the fuel pipe coming off the sender all neat and tight. The TD5 tanks have an odd breather exiting the n/s of the tank which apparently lets air in. I have read numerous problems on the net regarding water ingress to the fuel tank etc etc. This is partly due to where they are located on TD5s. I have tucked mine up behind the weathershields amoungst the electrics for now, but have considered linking it into my extended breathers for the axle to make it watertight. Photo 11 shows what the pipe I mean.

Next step is to run the fuel hose which comes off the sender along the chassis rail and into the pump. Note, I have placed the transfer pump near the existing tank due to it being slightly better protected. You can mount the transfer pump wherever you like, but here ticked all the right boxes for electrical feeds, out of harms way etc etc. At this point I have also taped the + & - wires from the sender unit to the fuel pipe and run it all as 1 along the top of the chassis rail. photo's 12 & 12a show how it was originally and how it is now. Here I have also placed a 1 way valve followed by an inline filter. photo 13 shows the solid state transfer pump installed, bolted through the seat box. The pump can run dry for a bit, but the purpose of the 1 way valve is to allow it to hold fuel in the filter and immediate pipework. A filter is a good idea also (cant have to many ). From the outlet of the pump you should run pipework to that little 90 degree bit on the filler that points down the original tanks filler. (i have added an extra photo of the filler from a diff angle to show this).

next you should install the Y piece filler and plumb in the filler hose and breather on both the Aux and the original tank. Photo 14 shows the filler in place with original pipework on. I have then taken the new filler over the spring hanger to link into the TD5 tank.

Where the pipes and wires are near the original fuel tank I have earthed both the sender and pump to a common earth on the Gearbox and taken the feed for the pump and the + sender along the chassis rail and up into the engine bay where they enter the bulkhead and into the dash. Now I have a mudstuff dash so just wired in another (carling) switch to operate the fuel pump. As the pump only draws 3-4amp the switch does not require a relay (carling switches are rated higher). You could install a switch here, or alternatively on the dash binnacle there is a black plate on the lower right (underneath) which you could use. or again put one in the seat box right next to the pump. The sender wire then go's into your seperate gauge Photo 16 (I removed the clock and installed it into the mudstuff) which you can take a feed off the others for.

And that is it. The dash switch operates the pump which draws fuel from the TD5 tank and spits it out down the original filler (photo 15). The Y piece filler keeps it looking original and allows both tanks to be filled from the same point. The seperate gauge also fires up from the ignition and works just like the original.

I hope this guide has helped clear the air a bit, Its a little vauge on specifics, but as you get the bits together you will find what you need along the way. Its a long process, but once its in, its a trick bit of usefull kit. The TD5 tank has a 60 litre capacity which is 10 litres more on top of your original underseat tank (50L) So your overall capacity is now 110 Litres.

This has given me an unaided range of ~650/700 miles depending on road conditions. An excellent upgrade for those with overland prepared 90's.

Enjoy.

G