Twin Tank Options?

[ajh]

I am working on a Series/200TDI conversion and the vehicle has dual-tanks (they were filled from each side; I'm converting to use a single fill-point. The stock switch is obviously for the 2.25HO and single feed-line. What is the easiest way to set up the system with the 200TDI so both the feed and spill return lines switch at the same time. One person suggested two electric switches; but I'm hoping for something mechanical and straightforward.

[Les Brock]

Miitary Fuel tank changeover switch ?

http://www.lrseries.com/shop/product/listing/1068/110/1/526783-MILITARY-FUEL-CHANGE-OVER-TAP.html

[Team Idris]

On the face of it, it sounds like a daft question?

If you have one filler you need a pipe at the bottom of the tanks that join them together.

But I guess you are going to 'T' the filler ports, with no bottom balence tube? In which case, it is two 3-way valves.

For the lack of nobbin' around though, I would seriously consider a bottom ballence tube. There are many good bulkhead fittings out there that you can fit into the tank with a drilled hole. 10mm bore would do but 13mm would be better.

Unless you plan to drive distance on side slopes, in which case all the fuel will go into the tank without a pick up pipe. Then you are back to two hand valves

Personally, I'd 'T' the filler so it filled both to the top, but fit all the engines pipes to the tank nearest the filler neck. Then electric-pump the fuel from the second tank to the first as needed. No valves to mix up and one switch. Simples

[Daan]

I would stay away from the bottom pipe: if you rip it off when offroad, you lose the contents of both tanks. I would T the return to both tanks, and have a single switchover valve to the suction line. It might return to both tanks while empty, which is not ideal, but it is probably the most reliable. I personally would stay away from the electric pump idea, as it is yet another system on your car that can fail.

Daan

[tacr2man]

have one main tank which handles supply and return , then have second tank with pump to main , its worked for me for more than 40 years , and never had pump fail yet . If the pump did fail you can always siphon fuel out in emergency , or even undo tank drain and let it run into bucket , gravity is very reliable

[Dave W]

The Pollak 6 port motorised valve works really well, I used one for my dual tank setup (TD5) although I also used two fillers so the two tanks are completely independent.

It swaps the feed, return and fuel tank sender over using a switch on the dashboard.

[bluespanner]

On trucks you have one tank with the feed and return that is none vented, and the other tank vented and fitted with a normal stack pipe, up and over in to the top of the standard tank. Idea being that as the fuel is used in tank 1, the vacuum created draws the diesel from tank 2. Hence on a recent trip to Italy, my fuel gauge got to 3/4 and stayed there for the remainder of the trip.

No pipes underneath either.

[Snagger]

Have a look here to see the genuine LR system for feed and return line selection for twin tank diesel systems: http://www.nickslandrover.co.uk/air-filterfuel-tap-linksbonnet-lining/

It uses the standard petrol feed valve, but has a linked return valve operated by the same lever movement as the feed valve. They're not cheap or that easy to source now, but they are out there. A cheaper alternative would be to use two second hand feed valves from broken ex-MoD vehicles, which give you the option to return unused fuel to the same tank or opposite tank from the feed, as required - useful for balancing uneven tanks, feeding from a leaking tank and returning to a good one, or for purging the vegoil by delaying the return line change over on a dual-fuel system.

Don not be tempted to return to one tank only, as this could overfill and spill fuel onto the road, and don't cross-connect at the bottoms as firstly, it could cause a loss of all fuel if damaged, and secondly, would result in unwanted fuel transfer to the downslope tank when driving or parked on side slopes, which not only causes CoG problems but could cause fuel starvation when driving with the upslope tank selected. You could get around both those issues by having cross-feed valves, but that's just another expense and complication.