Not one, but Two?

[Chris_in_Ravenswood]

Hello, you lovely people!
I have a D21 TD27T dual cab 4x4 and I recently changed the 60L Diesel tank for an 80L tank out of a donor vehicle. (If you want to see how that went, look here: http://www.navara.asia/showthread.php?t=24622)

The 80L is all in and working, the bash plate is on and it is doing exactly what it should. I was looking at the 60L tank and thinking about flipping it around and installing it opposite to the 80L, on the near-side of the truck. I have all the mounts (and I would have no worries modifying everything to fit).

The real questions are:

1) Am I breaking any laws if I do this?
2) Do I keep EVERYTHING separate up to the engine (where I have a tank selector valve, or something) or do I connect them together and use the 60L as a slave to the 80L?
3) Do I use the fuel pump in the 60L as a transfer pump into the 80L?
4) Do I keep separate fillers, or T off after the filler neck to both tanks?

Has anyone done this? I had a look around to see if I could find anyone that had done this, to no avail.

If so - How did you do it and what obstacles did you face?
I will need to "centre" the 3" tailpipe, as it is in the way at the moment.

I just figure that I have most of the bits and I can choose to fill up with up to 140L without having to worry about cans.

That has GOT to be useful, hasn't it?

What do you think?

 

[Old.Tony]

Legally a passenger vehicle or light commercial vehicle can carry up to 250L of fuel. That means have fun!

Not sure how to actually plumb them together. I have a Long Ranger which is an additional tank to my OEM tank. The way it's set up, I can't tell how much fuel I've used out of the system until the needle starts to move and then I know I'm eating into my "main" tank (70L down, 80L to go). That may or may not suit you and if it does I'll go have a squiz at how it's connected (it's raining rather heavily right now though and we're camped in a forest).

 

[bods]

No reason you couldn't do it... The patrols that had 2 tanks had a y piece in the single filler pipe, they also had a transfer pump to top up the main tank. Its really up to you how you want to plumb them though, whether you want 2 separate gauges to keep an eye on each tank or join the tank feeds to the injector pump so it uses each tank at the same time and just use the gauge from the main tank.

The only problem you may have with joining the outlets is the size difference. You could probably also join the injector pump return line so it feeds both tanks, but how well that would work I couldn't say...

You might be better off doing as you suggested and using the pump as a transfer pump and running a separate gauge for the other tank...

 

[Chris_in_Ravenswood]

Legally a passenger vehicle or light commercial vehicle can carry up to 250L of fuel. That means have fun!<<SNIP>>

Cheers for this. Another question answered and therefore, another tick in the "Can-do" box...

If you don't mind taking a look, that'd be great, but don't get wet on my account.

Have a great trip!

 

[Chris_in_Ravenswood]

No reason you couldn't do it... The patrols that had 2 tanks had a y piece in the single filler pipe,
<<SNIP>>

Cheers, Bods.

It's a toughie - If I keep it all separate, I can survive a punctured tank, a fuel pump failure and even a fill of duff fuel (if I'm lucky). I also fly little aeroplanes and I quite like the idea of a backup system.

So - If I have EVERYTHING separate (including the returns and filters) and have a tap that will switch over the fuel AND the return AND switch off the pump in the unused tank AND have separate fuel gauges for each tank, this gives me the most survivability??

And, if it does all this - IS IT WORTH IT???

Alternately, I tee everything together and have it act as a single 140L tank.

(Feels like I am missing out, though...)

P-H-E-W This job is getting harder and I haven't twisted a spanner yet...

 

[unkn0wn]

Hey

Ive been toying with this idea in my head, ever since you told me the Ute tank was bigger.

if you want them indipendant it might be worthwhile looking up the 6 port fuel selector valves
http://www.ebay.com.au/itm/42302-42..._Parts_Accessories&hash=item2582d0204c&_uhb=1

as they have the both sender you could wire in a switch to change the dash Fuel reading from either input so you go an idea whats in each tank.

 

[Old.Tony]

It's a personal belief of mine - and experience has proven it time after time - that the more complex you make something, the more risk of failure. Some redundancy in some things is nice - twin engined aircraft come to mind there - but for the fuel storage of a single engine, my preference would be to remove as many joins and factors as possible. So much, in fact, that we discussed a single 150L tank as a replacement.

Balancing that with the fun you have doing it yourself is your own challenge - but I would recommend simplicity over anything else. Makes field repairs less dramatic too.

 

[Chris_in_Ravenswood]

<<SNIP>> Some redundancy in some things is nice - twin engined aircraft come to mind there <<SNIP>>.

Cheers, Old Tony.
Ha! My flying instructor told me that the best use of the second engine (once the first one has failed) is to get you to the scene of the accident quicker...

I had the ignition system on the plane I was renting fail once (defective magneto) and I was REALLY glad that the second ignition system was isolated and independent from ignition switch to spark plugs.

That being said, simple is often better. Certainly a lot to think about.

I think I might just get the tank in there and see what solution "shouts loudest" The one that makes sense as the "best fit" in the circumstances is often the best solution, easy or complex.

Isn't this fun?!

 

[Chris_in_Ravenswood]

<<SNIP>> if you want them indipendant it might be worthwhile looking up the 6 port fuel selector valves<<SNIP>>.

Cheers for this - that's an interesting switch and I'll take a look and see.

 

[bods]

The only issue I can see with setting it up that way is the risk of an air bubble when switching between tanks, unless both tanks have pumps in them, or inline pumps on the tank side of the solenoid. That and needing to be sure you have enough fuel in the other tank before switching, which would be easier to monitor with 2 gauges...

As for the risk of air in the system, you might need to have it set up to either prime the line to the solenoid first (not sure how you'd go about setting that up) or have a bypass valve on the tank side of the solenoid and run the pump full time. I guess that would work for setting up a way to prime it first too

Unless the solenoid already does all that....... I couldn't say as I've never looked into them that much...

 

[Old.Tony]

What if the second tank had a pump that transferred the fuel into the first tank, the first tank had an overflow that fed into the second tank ... fuel pickup in the first tank, either or both tanks could have fuel gauges. The only time air would get into the system is with a fault or if you allowed it yourself.

The pump wouldn't have to be a high flowing pump, and I'd aim it away from the fuel pickup. Diesel is foamy and could aerate around the pickup in the first tank causing air bubbles in the lines.

Potential failures:

* Either of the lines between the two tanks (tank2 to pump, pump to tank1, tank1 to tank2). Remedy: clamp it and continue with the main tank.

* Pump. You're left with the main tank.

* Fuel pickup - well, we're getting into "normal territory" here so I'll stop.

Basically any failures in the secondary system would simply leave you with the primary intact - still good to keep going.

 

[bods]

What if the second tank had a pump that transferred the fuel into the first tank, the first tank had an overflow that fed into the second tank ... fuel pickup in the first tank, either or both tanks could have fuel gauges. The only time air would get into the system is with a fault or if you allowed it yourself.

The pump wouldn't have to be a high flowing pump, and I'd aim it away from the fuel pickup. Diesel is foamy and could aerate around the pickup in the first tank causing air bubbles in the lines.

Potential failures:

* Either of the lines between the two tanks (tank2 to pump, pump to tank1, tank1 to tank2). Remedy: clamp it and continue with the main tank.

* Pump. You're left with the main tank.

* Fuel pickup - well, we're getting into "normal territory" here so I'll stop.

Basically any failures in the secondary system would simply leave you with the primary intact - still good to keep going.

In saying all that, I guess it would also be possible to have the spill valve line return to the second tank too... Facet make pretty decent transfer pumps, so that may be another option to look at... Maybe you could use the original fuel return line as the inlet line for the transfer pump...

Maybe I should look for another stock d22 fuel tank to drop into the other side of mine and move the exhaust too...

 

[Chris_in_Ravenswood]

Hmmm.
I have had a lot of input from this forum along with others (and a few I have met out and about!).

Here is an updated list of requirements:

I should use the second tank as a secondary storage unit and not connect it into the primary tank - This protects me if one tank gets a hole in it, or a fuel line splits, I don't lose all the fuel.

Have a ball valve that switches between the output of each tank - Assuming neither is allowed to go completely empty, I should be able to choose at will, via a simple valve. Ball valves don't tend to let in air. If I am smart regarding height/position, I should be able to make it auto-purge.

Have an electrical switch linked to the ball valve - Using a relay, this can select which lift pump in which tank is operating (so the one that is off isn't pumping into a dead-end) and this can switch over the fuel tank sender at the same time. (A momentary push-button switch could also be incorporated so it is possible to check the level in the other tank WITHOUT switching over to it).

Have BOTH return lines go back to the primary tank (but via a valve, just in case the primary tank has a hole in it) - The returned Diesel can go back to the primary tank. This reduces the complexity of the control on the dash. Use the main tank, when it gets low, switch to the second tank. If that gets low, switch back to the main tank and there is a bit more in there than you remembered. Thinking a bit more on this, I realise that I have no idea the rate that this will happen. Will it return 1L per hour while the engine is running, or will it transfer the whole secondary tank (apart from what it has used) in 10 mins of run time. Anyone got any ideas on this???

This can also act as a transfer pump on the fly (but only one way). Not ideal, but this is as far as I have thought it so far, so will probably change.

The chassis mount for the tank should be modified to fit the chassis AS-IS (ie, without modifying the chassis) - If I can re-use existing holes, or threaded inserts, that's great. Otherwise, it'll clamp on. This means I can't compromise the chassis by welding or drilling. Spacers inside the chassis rails will stop any compression if I use a pre-existing through-hole to bolt to, or I can spread the load if a clamp-type fitting is used.

So - does that make sense?

What have I missed?????

 

[Old.Tony]

Makes a lot of sense. Not sure I'd return fuel to the primary, I'd return to the tank being used, because that would truly simplify things: you press a changeover button and the pickup, return and fuel gauge all switch to the alternate tank.

I don't think the D21s had a huge fuel flow rate - nothing like the CR diesels, which can turn over 80L in a few minutes, but I'd still return fuel to the working tank.

The changeover system does introduce an additional layer of complexity, but you add that to score redundancy so it's a balance that you choose.

 

[Bryce]

Why don't you go to a wreckers and grab a changeover solinoid from a landcruiser with duel tanks. They are an electronic controlled changeover valve that operates both supply and return lines. This way you wont have to worry about what tank the return goes to and you can use standard outlets for what they are designed for.
As far as the fuel gauge goes a simple changeover relay will let you switch what the dash is displaying.

 

[Chris_in_Ravenswood]

Why don't you go to a wreckers and grab a changeover solinoid from a landcruiser with duel tanks. They are an electronic controlled changeover valve that operates both supply and return lines. This way you wont have to worry about what tank the return goes to and you can use standard outlets for what they are designed for.
As far as the fuel gauge goes a simple changeover relay will let you switch what the dash is displaying.

Cheers, Bryce.
No wreckers I can find in WA have even HEARD of the changeover solenoid... When I explained it to a couple of them, they said things like "Oh - The fuel switch - No, wouldn't have one of them, try ARB"

I could use one of these, but (from what I have seen on the net) it only switches the supply, not the return (but I could well be wrong!)

My primary concern is working out what to do. The "how to do it" should just fall out of the "what to do". (Or is that just a bit too optimistic???)

I can't thank you guys enough for helping out.

Cheers!

 

[hardalada]

As the proud owner of a 1991 Terrano 2.7TD and a 1972 Jaguar XJ6, may I take the opportunity to ask you to consider not reinventing the wheel, and nick the tank selector switch and the return valve system from any series 3 fuel injected XJ6, which you will find will allow you to connect up both tanks separately, as the dashboard switch has provision for automatically switching the fuel sender readings as well as the appropriate return valve and uses only the one fuel gauge.
There, sorted, two independent tanks feeding into one line, using non return valves to ensure no cross feeding on output, and automatic return valves selection electrically activated by one neat rocker switch, and only one fuel gauge needed!

For those that wonder why the Jag has two 54 liter tanks and two fuel pumps and two fuel level senders.It's because it is not very economical, and if the tanks were interconnected and you parked on a slope the higher tank would drain into the lower tank and overflow it. Then it would be even less economical...and a fire hazard!
It also comes in handy when the drain tube for the well in which the fuel caps sit blocks up, it rains, and the fuel tank fills with water.
After draining a liter of water from each tank, I fitted a double CAV 296 filter head with sedimenters.....diesel technology on a Jaguar.?....

 

[Chris_in_Ravenswood]

... snip... may I take the opportunity to ask you to consider not reinventing the wheel ...snip...

Cheers, hardalada!
I thought inventing the wheel was tough the first time around and I'm not about to have a go at improving on it....

THIS is why I asked the question!!!
When would I come across a Jag?

Only problem for me is that I live in Western Australia and the scrap yards over here make you wear a dinner jacket and pay a $50 door charge just to walk in the door...

I can imagine how it'd go if I called them -

"You want bits for a JAG??
That's going to run into the tens of thousands - and that's just for the rocker switch!"

 

[04HUG]

G'day.
I have an older 2.8 Hilux with duel tanks. I needed a 'mod plate' when the rego was transferred to QLD. They are independent up to 2 x3 way ball valves just before the fuel filter. I need to pop the bonnet to change them over. one valve is supply the other is return. If I only change one valve then I can transfer from one tank to the other (in either direction). I run the original fuel gauge with a toggle switch to select what tank fuel level sender to use.

KISS is a good principal with this application.

I could set up the Land Cruiser changeover valve so I don't have to stop, but by the time one drives for a tank of juice you need an excuse to stretch the legs.

 

[Chris_in_Ravenswood]

G'day.
... snip...
I needed a 'mod plate' when the rego was transferred to QLD.
... snip...
2 x3 way ball valves
...snip... .

Thanks 04hug!
This sounds like what I am after.

2 questions (and excuse me being a Pommie for the first one) -

1: What is a mod plate?
2: Do you remember what the valves were / where you got them?
Manufacturer and part number would be ideal, but whatever you can remember would be great.

Cheers and have a great weekend.