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OE Toyota Auxiliary Fuel Tank Instal

27K views 62 replies 19 participants last post by  i12c 
#1 · (Edited)
G'day,
Finally got my OE aux fuel tank installed.
I'll preface this thread, by saying that to do this in North America will be difficult and probably not cost effective, due to the shipping costs involved.

Background.
Until 2013 the FJ was a single tank machine, finally the International market received dual tanks. 72 litres main tank and another 87 litres in the Aux tank.
Slightly used 2nd hand Aux tanks are now becoming available down under as owners swap to bigger tanks, or to LNG - dual fuel options, and ditching the OE aux tank.

Depending on the age of your FJ, the mounting points may or may not be already in place in the frame and underbody to mount the tank. Any FJ built before mid 2012 will not have these mounting points fitted. My 2011 didn't - so I had to create the mounting points as well.

So 6 months ago I picked up a lightly used / almost new Aux tank.
Complete with tank, mounting brackets, tank straps, skid plate, and sender units for both the primary and Aux tanks - out of a 2013 built FJ. The owner had removed the Aux tank to fit LNG. So I got a 90% complete system. The only pieces missing were the hoses, and the filler pipe with the Y - to fill both tanks.

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After months of research and talking to many people and companies, I came to the conclusion that I would not be able to totally duplicate the OE system. The OE system is a pressure / gravity feed system, that syphons the fuel from the Aux to the Main continually ..... and uses a single dash gauge to read and show the contents. The sender units combine and are read by the fuel ECU.

So I compromised and accepted the prevailing consensus to fit a pump and manually transfer the fuel from Aux to main. This method is tried and proven down under for many years, and is an easy instal for a professional. No one wanted to attempt to replicate the Yota method - let alone touch the OE wiring harness .... and in hindsight I agree. Using a pump and keeping the Aux as a stand alone system has its benefits.

I purchased a new Y filler pipe from Yota, but this isn't really necessary, as a professional can tap and solder in a Y fitting just as easily.

to be continued....
 
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#2 · (Edited)
So onto the install ...

1. fitting the mounting points into the rear cross bar to mount the brackets.
I marked and drilled 10mm holes into the underside of the cross bar - using the bracket as a template, then marked with a hole punch the inside of the top of the bar for each hole I had drilled. This gave me reference point to drill out a 30mm hole- with a step drill bit - for each pair of bolts. This gives you room to mount AL braces inside the rear bar to take the strain of the brackets. The metal is not thick ..so I used 6 mm thick AL bar - as long as possible to spread the stress of the bolt mounts over a greater area.

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With the holes drilled and prepped and painted to stop any rust issues down the track, the two rear brackets were mounted. Then using the Yota pre-drilled holes in the under floor, made two more 30 mm holes inside the cargo floor - using the same method as above. With more 6mm AL bracing I used the straps were mounted. Step one complete...

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2. The tank itself sits on the two straps, the straps are secured via pins to the rear brackets.
 
#3 · (Edited)
3. With the tank fitted into position ..off to the professional to plumb it in.

I chose to let the professional plumb it in, because this is my DD, I needed it done quickly. But also for insurance, and compliance with our road rules...
The install went reasonably smoothly. But there were a couple of minor issues.
Because a pump was being used, the filler pipe had to be tapped and a fitting make and brazed into it, to accept the pump line.
This also necessitated a switch and gauge to be installed into the dash. I could not use the OE dash gauge as splicing into OE harness was considered a dangerous option.
This lead to another challenge, the OE sender unit is not compatible with the gauge, the ohm reading are reversed and at a different level. So at this point I do not have a gauge to read the Aux tank level.
Not sure this is a big issue or not, I may still fit a working gauge once I figure out if I really want one, and can make the ohm reading work, with the OE sender.
It was deemed not viable to swap the sender out, with a different type of sender unit, as Yota use there own size n type of sender unit - not a standard size or fit... a yota size and fit.....
Keeping the Aux separate to the OE system also meant I did not have to drop the main tank and swap senders - a dual tank system using a different sender to a single tank system.

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#4 · (Edited)
The end result, two separate tanks connected with a pump. Holding a total of 159 litres of juice.

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The 2nd last step was to fit the tank skid.

This was painted prior to fitting with my customary VB signature touch. :rofl:

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It should also be noted that a hi tuck exhaust system cannot be used with the aux tank, there is no room.
So I had to swap out my BA Muffler hi tuck and go back to stock.

And finally last step. Fill er up .... took 139 litres first fill .....

Expected range for DD, is estimated to be 1000 - 1200kms (600-750 miles ) , upto 1400kms ( 900 miles ) long haul driving.

I will add some more pictures, shortly.

Total cost for this project, around the USD$1000 mark, I don't have an exact figure.
Installation by the professional was more than expected, due to the issues not for seen, but anticipated.
By using the existing filler pipe would have saved $200 - with a trade off in cost to modify it to a Y filler pipe....

Cheers
Baz
:blueblob:
 
#5 ·
Very interesting thank you. I've been looking at the underside of mine and wondering if a tank from a 150 series would fit straight in. Would you have any idea? (mine is a 2014 so on the 15 chassis). I can get a 150 tank off an accident damaged car no problem, if it is a frontal then the tank will be 100%.

Though the underside of mine seems to have what I assume are the 150 tank mount points in place there is an ECU or something directly above where the tank would sit?
 
#7 ·
G'day mate,
Thanks.
I don't know if it would fit or not, although the FJ and Prado share chassis' sand many similarities ... The Prado 150 aux tank could be different .. Probably is.
I also seem to recall the Prado dual tanks are set up in reverse, with the main tank actually behind the axle, with the aux in front ..... Another issue could be the size of the Prado tank, being larger in capacity, and therefore a different shape and size.
The ECU / charcoal canister can be moved, but that's another step in the process.
Still worth investigation.....

Cheers
Baz
:blueblob:
 
#6 ·
Looks good Baz. It's nice you guys have that option down there. I like the Bozo license plate too............>:D
 
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#11 ·
Hi Baz, Good day, you might want to sent this info to Izalusky (snow leopard),
who is looking into outfitting oem setup and making it happen this side of the pound. I am thinking shipping these used tanks via oceanic freight will be cheaper and from your mention of cost around $1000 is not bad at all.

Great info and awesome that you were able to make it work.
Cheers.
 
#18 ·
Thank you Baz for the very informative write up on refitting an OE aux fuel tank to an AUS FJ. :bigthumb:
As Baz alluded in the first post, this mod is difficult and not very cost effective for North American or other markets that require very stringent emission control. I've mentioned before in lzalusky's build thread that the major hurdle in adapting AUS aux fuel tanks (either OE or aftermarket) to the American FJ is the space taken by the charcoal canisters. As you can see in the photo below, the charcoal canister for the emission control system takes up quite a bit of space under the cargo floor. The closed-loop emission system is also very sensitive to leaks. It may be possible to relocate the canisters and use the AUS aux tanks as is. The alternative would be to have a smaller US version aux tank made (aftermarket); I've sent the pertinent dimensions of our canisters to the Long Ranger company at their request but so far they have not pursue a US version of the TA71 aux tank. I suspect the small quantity demand and high shipping cost to the US may be the major factor for them to go further.



Modifying the OE aux tank is challenging as all the tank plumbing are located where the big charcoal canister is in the US model (see Baz's photo below). So, for an OE aux tank solution for the US version, we can probably only use the OE Y-filler pipe which may be purchased from AUS aftermarket companies as well. As Baz mentioned, refitting the complete OE electronics will be very difficult (but not impossible IMO).

 
#20 ·
G'day,
Thanks TC, very well put.
I agree, I am sure it is possible, although not a cheap option.
The physical relocation of the canister is necessary, and use of either an OE Ypipe, or aftermarket Y pipe.
LRA do make a nifty dual pipe, with smart breathers.

Figuring out the electronics is hard for a lay person like me, but easy for those learned in electronics.... Another issue I encountered was trying to source the harness side connector for the sender unit. Yota would not / could not supply this connector. I was not able to locate this odd shaped connector from other sources, so a home made solution is needed.

The two tank senders run at different ohm measurement, and combined give the correct level at the gauge.... Just another complication.
It's also possible that a different fuel ECU is used in the twin tank model, but I did not investigate this.

Still I am happy with the result, and thankful to have plenty of juice now.

Cheers
Baz
:blueblob:
 
#28 ·
G'day and great stuff, Baz. Got a couple of questions if you know, since your plumbing was done by a tech. I have an aux tank fabbed up for my 08 FJ, and want to keep it simple...just transfer to the main via pump. No aux gauge needed. I assume from your reference to the "Y" fitting, that the main fill pipe is cut, and "Y" inserted to fill both tanks at the same time. Easy....my concern is where to tap into the vehicles vent line and the point in the system at which the re-fill line is attached going to the main.
Can you offer any help for me?

Thanks!

Mark
 
#29 · (Edited)
G'Day Mate,
There are two ways to go about it.
1. Get an OE Y pipe which has the Y built into it - so its splits the fill between both tanks. or cut and insert a Y into a single tank filler pipe.
The end is basically the same result.

For the breathers, there are several factors to consider. Depending the on the setup and an regulations and sensors already fitted to meet CARB testing etc....

If using an OE Y pipe the breather is a smart breather built into the pipe, so both tanks vent thru the single breather. Its a one way breather so petrol or water etc cannot flow back into the tanks thru the breather tube, goes only one way ... out type thing. With OE aux tank, you plumb the main tank and Aux tank together and the actual breather is on aux tank, up the neck towards the filling point.

The pump is obviously hooked up to the aux tank, and pumps fuel back towards the main tank, so we tapped a fill hose ( pump output ) into the main filler pipe near the main tank. it meant drilling tapping and brazing a knuckle into the filler pipe far enough forward so it did not fill backwards to the aux tank - in an endless loop, so the pump pushes the fuel into the main tank.

IF you had twin OE tanks, then Yota have a 3rd pipe on the main tank to receive fuel from the Aux tank. But as the single tank model doesn't have this third pipe we had to make a connection into the filler pipe.
If that makes sense.

The pump sits up high up pretty much above the rear upper links ..out of the way, so the fuel actually gets pumped upwards / or sucked upwards into the pump, then back down towards the main tank.

The OE Y pipe is pretty flat n level, so once the main is filled, any additional fuel run backwards into the fill of the Aux.

LRA do make a Y pipe to suit as well, or you can just cut the original filler pipe and insert a Y joint, either made from rubber hose, or a metal Y ....

FYI, the OE Y pipe is about AUD$300 locally down under, so its not a cheap bit of pipe ... :lol:

Hope this helps,

Cheers
Baz
:blueblob:


ps. this system with the breathers is legal and OK down under..... but I am unsure about the needs / regulations in the US for this set up..... as you have additional charcoal canisters too and vapour sensors etc...... it might take a bit more work to make it pass any inspections and not throw codes ...


Good luck
cheers
Baz
 
#34 ·
G'day,
Thanks...
No I have not been able to figure out how to run the OE sender to the after market fuel gauge or to the dash gauge.
So I am running on memory, when I transfer fuel ..... ( 2 litres per minute transfer rate )
The OE sender ohm range for the aux tank is Full @ 66 ohm / Empty at 210 ohm
The after market gauge uses 0 ohm for empty / 90 ohm for full ....
so without electronic voodoo gadgets to convert signals its out of my capacity....

cheers
Baz
:blueblob:
 
#36 ·
G'day,
no probs mate.
The only challenge is that aussie part numbers are different to US part numbers, and you would not be able to order them anyway as US dealers don't have access to them...
But I'll post up the diagrams and part numbers next.....

Cheers
Baz
:blueblob:
 
#40 ·
Hi guys - Another option might be the OE kit from Gulf spec FJs.
I have no idea if there is a charcoal filter in there (i suspect not, as my tank sizes are the same as Baz's), but shipping might be better/cheaper and the Gulf dealers are probably quite happy to ship.

I'm just guessing all this though. try Al-Futtaim (toyota.ae) and see how much they'd charge to ship to you sea or air freight.

Parts Sales Centre, Al Badia
Saturday-Thursday: 08:00 am - 08:00 pm
Friday: 08:00 am - 04:00 pm
Tel No: +971 4 706 2777
Fax no: +971 4 256 5790
Email: toyota@alfuttaim.ae
GPS Coordinates: 25 12' 526'' N 55 21' 690'' E
 
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