Auxiliary Tanks, How did you install yours?

[braddonfire]

So when I bought the car (1993 NH) It came with an auxiliary tank (not installed)

It's been floating around my garage taking up room for too long now and I've decided to throw it in.

I was hoping to get some discussion on how everyone has installed them or seen them installed in other cars.

I was thinking of possibly running the two tanks on independently of each other, separate fillers, separate gauges, maybe even separate pumps? Any opinions on the pro's and con's of such a system?

[stevemc181]

I think you will find most of them are set up as separate tanks and they use a transfer pump to pump fuel from the Aux tank into the main tank. The fillers are usually a dual throated connection that attaches to the normal fuel filler. So you basically have two holes when you open your fuel cap and can fill either tank.

Mine was installed by TJM, so can't advise on the install method, a few on here have done their own though. Mine just has an Led Indicator gauge that flashes red when the tank is empty and has different level green lights for 1/4, 1/2 full etc. The pump just pumps it from the Aux tank up into the filler neck of the main tank, and takes around 30 minutes to pump 60 litres over.

[geopaj]

I think you will find most of them are set up as separate tanks and they use a transfer pump to pump fuel from the Aux tank into the main tank. The fillers are usually a dual throated connection that attaches to the normal fuel filler. So you basically have two holes when you open your fuel cap and can fill either tank.
.

This is how I did mine. I also used a change over relay so that the 'main fuel gauge in the dash' reads the fuel level in the main tank, but when the transfer pump is running 'main fuel gauge in the dash' reads the fuel level in the sub tank.

[Uncle Fester]

I have never had Aux tank in a car other than a LPG and Petrol on my old NM. The one thing I did like was if I punctured one I could run off the other so I like your idea of two totally seprate systems in case you ever did puncture one or get a bad batch of fuel.

[braddonfire]

This is how I did mine. I also used a change over relay so that the 'main fuel gauge in the dash' reads the fuel level in the main tank, but when the transfer pump is running 'main fuel gauge in the dash' reads the fuel level in the sub tank.

I was thinking this would be a good way of displaying the two tanks, I flick a switch, a little LED turns on next to the gauge that tells me I'm running off the reserve tank and the gauge now shows what's left in there..

I didn't want a second fuel gauge like a lot of the Dual fuel cars have, cluttering up my dash.

I have never had Aux tank in a car other than a LPG and Petrol on my old NM. The one thing I did like was if I punctured one I could run off the other so I like your idea of two totally seprate systems in case you ever did puncture one or get a bad batch of fuel.

That was the main motivation behind trying to keep the two as separate as possible, If something happens to the main tank. I don't want to be completely stuck.

[geopaj]

Two complete systems is ultimately the best setup, I think.

However, it is much more complicated and costly. If you go for two complete systems you will also need some way of swapping the fuel return line between both tanks. (Multi port solinoid?)

My sub tank will take the sender/pump assembly from the main tank if I ever need to run the sub tank as the main tank. This gives me some additional reliability.

I also have an additional filter (just a cheap $7 Ryco generic filter) between the sub and main tank. This means that if I am anywhere remote with suspect fuel I can put it into the sub tank and"pre-filter" the fuel by transferring it into the main tank.

[schnitzel]

I've done a few of these and they are different in setup between the petrol and the diesel, diesel can be setup as an auxiliary using a changeover switch which swaps between the two tanks, petrol is setup as a sub tank with the smaller tank transferring to the main.

Reason is the prohibitive cost of fuel cut offs you need ( and you need 4) if you want to run it as an auxiliary. The solenoids generally available simply do not cope with the pressure of a petrol efi system which has the pump in the tank, they fail and leak quite quickly as the pressure is too much for them in the reverse direction from the operating pump.

Had long discussion on this with the guy from lra in lilydale before I did my first one and was shown a few who had tried to do it and failed.
Only solenoids that have been successful were from Toyota but were very expensive and impossible to find second hand. ( new price was over $350 per solenoid).

Will be doing another one today or tomorrow depending on weather on my current project as am putting a 135 l lra tank and a 45 l sub in my own nj.

[Madmen]

I've done a few of these and they are different in setup between the petrol and the diesel, diesel can be setup as an auxiliary using a changeover switch which swaps between the two tanks, petrol is setup as a sub tank with the smaller tank transferring to the main.

Reason is the prohibitive cost of fuel cut offs you need ( and you need 4) if you want to run it as an auxiliary. The solenoids generally available simply do not cope with the pressure of a petrol efi system which has the pump in the tank, they fail and leak quite quickly as the pressure is too much for them in the reverse direction from the operating pump.

Had long discussion on this with the guy from lra in lilydale before I did my first one and was shown a few who had tried to do it and failed.
Only solenoids that have been successful were from Toyota but were very expensive and impossible to find second hand. ( new price was over $350 per solenoid).

Will be doing another one today or tomorrow depending on weather on my current project as am putting a 135 l lra tank and a 45 l sub in my own nj.

Hey mate how did you with the install on your nj? I've been given an lra subtank for my nj and were wondering how to install and set it up? Do you happen to have any pics?
Could be a long shot being an old thread.. but you never know.
Cheers Charlie.

[Turorit]

G'Day mate,

I've been putting a subtank in my NJ 3.5L over the last couple of months (long story....). Hopefully I can give you a few tips.
Mine is setup to pump from the sub tank into the main tank via the dual filler neck.

I've uploaded a bunch of photos to my google drive: https://drive.google.com/open?id=1BZ...hCqRSJcp1XUxe0

Issues I ran into:
- Fuel filter along the B pillar crossmember had to be unbolted and pushed upwards out of the way. Had to bend up a couple new brackets to hold it.

https://drive.google.com/open?id=1EjJaev8YqgR-RXFrJvx5Oubh7jLqlY7w

-There is a plate over the rear brake variable valve, this plate needed to be removed so it didn't foul on the sub tank fuel lines.

https://drive.google.com/open?id=1QzLZVe1UnuMnlaNLEQmh9f6Bdf65_z8K

https://drive.google.com/open?id=1hvwGFlbzCb8eaGnnPolcZTaPkaoiyA3B

-Handbrake cable attaches to a bracket on the floor pan. I had to unbolt the cable and bend this bracket out of the way. Subsequently I think my handbrake now needs some adjustment.

-Fuel hose- The Sub tank fuel pump outlet has a threaded BSP connection, I couldn't find a suitable adapter so ended up using 1/2" EFI Fuel hose (Repco, $12/m), sticking it onto the threaded outlet & hose clamping it. Hopefully it'll hold.

-Dual Filler Neck- This was the hardest part. I didn't want to pay some insane amount for an LRA neck so...
I found a dual filler from a 90 series Prado at the wreckers. The pipe is only 35mm so I had the local exhaust shop weld on some larger pipe so that the Pajero factor filler hose will slip onto it.

https://drive.google.com/open?id=1W2lCRtmHrZddtvaB4k7wx5P_v-ge8W19

-The prado filler neck doesn't have a flange to bolt onto the Pajero body, so I butchered the flange of another Pajero filler neck & had a friend oxy-weld it on to the Prado filler.

https://drive.google.com/open?id=1BzcSivgbgRLlaWnpsWmVvInHbPS_aGjb

-Prado filler has two smaller breather pipes, I had a 3rd pipe on to act as the fuel transfer port.
-Due to the thin metal of the prado filler & the plating on it, welding was difficult & I had to seal up some pinhole leaks using some Permatex Fuel Tank Repair Putty. Not sure on the longevity of the product, however it'll only briefly in contact with fuel during filling so it should be OK.

https://drive.google.com/open?id=1-cKZmujTC85H_7ekeC8XVL2MatvW3miz

-Fuel Gauge- I spent a while trying to find a fuel gauge to work with the subtank. The factory pajero fuel gauge reads 0-3 ohms as full, and 110 ohms as empty, opposite to every other fuel gauge around.
I took a stab at this cheap one from AliExpress which worked out OK.

https://www.aliexpress.com/item/Car-Fuel-Gauge-10-LED-Fuel-Level-Meter-Gauge-Fuel-Level-Sensor-12V-Motorcycle-Automobile-Aluminum/32821396271.html?spm=a2g0s.9042311.0.0.ddFZA8

-I bought a nice rocker switch & a timer delay relay to only allow the fuel pump to run for 15min.
-Relay- https://www.ebay.com.au/itm/12V-DC-Relay-Delay-Turn-off-Switch-Module-with-Timer-Electrician-Chip-Module-Cct-/172994273185
-Sub Tank Switch - https://www.ebay.com.au/itm/Rocker-S...72.m2749.l2649
-The wiring from the fuel pump runs under the carpet along the trans tunnel. To get the wiring in, above the subtank where the floor pan rises up towards the rear, there is a factory rubber bung. Remove & replace with a wiring grommet. Run wiring through some split loom tubing.

As for actually installing the tank....
-Interior- Remove rear seats and fold back carpet. Also fold forward the carpet in the footwells.
- Jack up the subtank into position & mark the holes to be drilled - I used some red spray paint.
- From here I drilled one bolt hole & repositioned the sub tank to put a bolt through before drilling the next hole. Time consuming but saves having to re-drill extra holes.
-Rinse & repeat until the tank is in. Cut some 5mm steel flat bar (150mm-ish long) to put under the bolt heads inside the car to spread the load over the floor pan.
-Local exhaust shop will need to bend up a filler pipe to run from the sub tank filler, along the vehicle chassis rail up to the filler neck.
- Plumbing the filler neck- Ideally have the breather hoses on top rather than underneath like mine. The exhaust shop bloke welded the pipes on crooked, so it didn't fit the way I wanted. Had to flip it around to make it fit:

https://drive.google.com/open?id=1ariGwqapL42QyOJuwBIE-zDv_oIiSsXG

Hope this makes some sense & is helpful.
I'm off to have a meltdown after recounting this traumatic experience