GU Auxillary tank

Submitted: Thursday, Mar 11, 2004 at 16:48
ThreadID: 11171 Views:2281 Replies:4 FollowUps:7
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A few days ago there was a post about a GU's transfer pump not working and one of the responses mentioned about changing over to a system similar to how Toyota's do their sub-tank set-up. As I understand it, with the Cruiser, you choose directly which tank you want the fuel to come from and that fuel goes directly to the motor.
As much as I hate to admit it, I reckon Mr Toyota might have handled this better than Mr Nissan.......the idea of transfering fuel from one tank to another seems a bit silly to me, especially if the main tank has been holed or contaminated.
So....has anybody bothered to do something about it? Is there a fix-it kit available? It probably not be worth doing anything with the little OE factory 30+ litre tank; you'd probably want to fit one of those 80 litre jobbies to make it worthwhile.
I would imagine it would be a solenoid or something and a "T" junction where the 2 tanks feed into the solenoid-operated switching thing-a-me-bob (I'm sorry if that term's too technical for some of you)...LOL.
Just a thought.
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Reply By: chrisfrd - Thursday, Mar 11, 2004 at 17:04

Thursday, Mar 11, 2004 at 17:04
Basically, you are correct on that count.

The Nissan system is really stupid. I think it was a political thing... Toyota says TomAAto, Nissan says TomAeto.

I've been working on a solution that is plug-and-play for a few months now.

The biggest problem with the system is that there appears to be tight integration of the factory system.. Something of which I'm trying to sercumvent now with some PIC processors and a little software.

Once I've figured that out and have figured out where to get the cable connectors for the factory's Molex connectors, then I might be able to let people know about the designs and such.

AnswerID: 49941

Follow Up By: Roachie - Thursday, Mar 11, 2004 at 17:14

Thursday, Mar 11, 2004 at 17:14
Mate, you're starting to make me come out in a cold sweat now with all this talk about PIC processors and stuff.....sounds like "electronics" to me. As I've said before, I have an inherent distrust of things that can go "physssst" in the middle of no-bloody-where; leaving me up the paddle without a creek. (that's why I got an old banger 4.2 t/d instead of the whizz-bang 3.0ltr electronic pootrol).
Is the fix you're trying to work on related to the 3.0lt or 4.2lt or petrol? If it is one of the newer technology type ones, then I guess there may be a need to integrate the fuel switch into the black box or whatever jiggery-pokery they need. But if it's the 4.2lt, I would have thought the switching set-up could be relatively simple for someone not all that much smarter than me.
FollowupID: 311756

Follow Up By: chrisfrd - Thursday, Mar 11, 2004 at 18:53

Thursday, Mar 11, 2004 at 18:53
Guess what????

Doesn't matter what the engine you have, the fuel controller system is EXACTLY the same!!!!

The flow-system is reasonably simple. It's basically a small 8-bit computer that monitors the fuel level in each tank and also monitors the push-button on the dash.

When you push the button, the computer sees if the sub tank has fuel in it, (30L minus 1.5L unusable fuel load that is retained for lubrication), if there is fuel, it then checks the fuel load in the main tank to make sure that it will fit...

If all is ok, the computer fires a relay and starts the pump. The computer also monitors the pump's tempurature and the pressure.

What I am intending to do is to make a little sub-computer, to replace the factory unit, that enables you to press the "sub-tank" button, switching the fuel from tank to tank.

A word of warning though! What I'm currently working on it wether switching fuel's mid-run will actually cause a drop in fuel pressure, with a subsequent error-code being dropped into the computer.

This system would be simplier, more eliquent and more importantly, free to any to copy (when I get it solid).

I'm doing this as an electrical engineering project for TAFE.....

FollowupID: 311784

Follow Up By: basecamp15 - Thursday, Mar 11, 2004 at 19:01

Thursday, Mar 11, 2004 at 19:01
Me too Roachie, go the 4.2!!
FollowupID: 311786

Reply By: Wayne (NSW) - Thursday, Mar 11, 2004 at 17:43

Thursday, Mar 11, 2004 at 17:43

The way I used to do a aux tank on a GQ diesel, was to fit a "6 port soleniod.

The way it worked,
From the aux tank, a pick up and return fuel hose would go to the 6 port soleniod
A pick up and return fuel hose from the main tank would also go to the 6port soleniod (6ps).
From the 6ps a fuel hose would go to the pump on the motor and a return hose back to the 6ps
A 2 way switch was fitted to the dash
In the main tank postion on the switch the 6ps would pick up fuel from the main tank and return the the excess fuel to the main tank.
The same would happen when the switch was in the aux postion, but would use the aux tank for pick up and return.

What I am not sure of is where is the transvere pump located, in the tank or outside. If the pump is inside the tank it might have to be removed and the pick up pipe extended to reach the bottom of the tank.

A 6 port soleniod should be avaiable from any 4WD shop that does tanks.

This set up will not work on petrol motors because the high pressure pump is located in the main tank, so all the fuel from the aux tank has to go through it.

If you are getting a larger tank fitted talk to the fitter and see if he/ she can fit it up the way I described.
If all else fails email me on the Member Msg.

AnswerID: 49952

Follow Up By: joc45 - Thursday, Mar 11, 2004 at 18:45

Thursday, Mar 11, 2004 at 18:45
Both systems are not without problems. My old GQ used the 6-port solenoid on the aux tank, but several times I had to remove it to clean the crap out of it after it jammed (fuel/tank debris). And it wasn't in an easy place to get at.
FollowupID: 311780

Follow Up By: Roachie - Thursday, Mar 11, 2004 at 22:18

Thursday, Mar 11, 2004 at 22:18
Thanks Wayne,
Once again you are a font of knowledge for me.
FollowupID: 311829

Follow Up By: Roachie - Thursday, Mar 11, 2004 at 22:22

Thursday, Mar 11, 2004 at 22:22
BTW, the transfer pump is located outside the sub tank, bolted to a chassis cross member immediately in front of the sub tank, practically under the driver's bum.
FollowupID: 311831

Reply By: Member - Peter (York) - Thursday, Mar 11, 2004 at 18:01

Thursday, Mar 11, 2004 at 18:01
Hi all , K&N Fabrications have a replacement tank for the GU which is a straight pump from either tank , it replaces the sub tank and goes right across the chassis ,their email they are in WA Kelmscott
AnswerID: 49956

Follow Up By: Roachie - Thursday, Mar 11, 2004 at 22:20

Thursday, Mar 11, 2004 at 22:20
Thanks Peter,
They will be worth a look by the sound of it.
FollowupID: 311830

Reply By: Member - Jeff M (WA) - Thursday, Mar 11, 2004 at 18:50

Thursday, Mar 11, 2004 at 18:50
Yeah I thought the Patrols would have gone that way because of an expensive computer controlled high pressure fuel pump or some such jobby. That's why they pump the fuel into the main tank so as to not have two expensive pumps. But then again I know absolutally nothing of these setups, JMHO from driving a 3.0l at work.
AnswerID: 49964

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