GU sub tank dash light

Submitted: Sunday, Mar 07, 2004 at 22:17
ThreadID: 11078 Views:7102 Replies:10 FollowUps:6
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G'day all, have a prob with the GU, the sub tank won't tranfer fuel and the light is permanently on the dash. Thought I'd check if anyone here has had the prob before reluctantly going to nissan. Their workshop manual (2 part) is $750.00 and the non genuine don't cover GU '98-'00. Any help would be great, mat
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Reply By: Wayne (NSW) - Sunday, Mar 07, 2004 at 22:46

Sunday, Mar 07, 2004 at 22:46

Assumeing there is fuel in the sub tank, the other thing it could be is the sender unit in the tank is either stuck on the bottom of the tank or the plug from the sender unit has come off. Not sure about the GU, but the GQ had inspection plates above the sender units. They were under the carpet directly above the tank.

The pump will not work because it thinks the tank is empty because the warning light is on. Fix the sender unit and the pump should work.

Check for fuses, but I don't think this is the problem.

If you can find the inspection plates, remove them and have a look at the top of the sender unit. Make sure the plug is still attached. If that is OK remove the sender unit. there should be small screws holding it down. Remove screws and slowly remove sender unit. A small metal box with wirers going to it should be at the top and a wire lever coming from thr box. On the end of the wire a float should be found. Make sure there is no holes in the float and the lever moves freely up and down.

With the ignition lights on, and the sender unit still wired up move the float wire through it's arc until the float wire is as high as possible, then check the fuel gauge again , it should have moved. If it has, that means the float lever was stuck in the tank some how, this you will have to check and fix.

Sorry I could not help further but I have not worked on a GU fuel tank.

AnswerID: 49468

Follow Up By: Michael - Wednesday, Mar 10, 2004 at 11:08

Wednesday, Mar 10, 2004 at 11:08
Good reply Wayne, thats what i think also, makes a lot of sense. Regards Michael
FollowupID: 311556

Reply By: basecamp15 - Sunday, Mar 07, 2004 at 22:53

Sunday, Mar 07, 2004 at 22:53
Could domeone actually tell me how the setup works. The only time my subtank light comes on on the dashboard is when i turn the car on and all the lights come on. After that it doesn't matter if I have the tank full, empty or draining, no light ever comes on the dashboard, only the green light on the sub tank button when it's on.
Also, my low fuel warning light does not come on so I have to keep an eye on the fuel. It's always been this way too.
Thanks, Mark.
AnswerID: 49469

Follow Up By: Wayne (NSW) - Sunday, Mar 07, 2004 at 23:59

Sunday, Mar 07, 2004 at 23:59
As I said before I have not worked on a GU tanks but I think this is how it works.

The fuel tanks have a float in the tank it self. It is attached to the sending unit and when fuel is added to the tank the float will rise up with the level of the fuel. This will cause the sending unit box (and I am not sure how to explain how it works but that is not important at this stage), to send a signal to the fuel gauge on the dash to show a reading,empty to full. The low fuel warning light also works off this float system. When the float has moved close to its lowest point, fuel tank almost empty, the warning light will come on. This is how I think it should work. If the warning light does not come on then the float might need adjusting.

Once the float has reached a low level the transverse pump will turn off so as not to run dry.

Again removing the sending units and trying them out of the tank through there full swing of the float with the ignition lights on.

I hope this answers your question, I know it is pretty general but there are not many ways a sending unit works.

FollowupID: 311286

Follow Up By: Roachie - Monday, Mar 08, 2004 at 09:56

Monday, Mar 08, 2004 at 09:56
Hi Basecamp15,
I know what you mean about the "sub-tank" light on the dash......I've often wondered the same thing as to what has to happen for it to light up under normal circumstances. I'm not sure that Wayne's response has answered the question, but he has surprisingly good knowledge of the Nissans considering he has a Tojo.....I guess it's from fixing faults when he's out on trips etc.
Touch wood, I've never had any problems with my sub-tank set up, but on one of my regular "lie-down & look-up" sessions under the Patrol a few months ago, I noticed the whole area around the transfer pump was caked-up with dried mud from a trip we did last October across country to Mungo NP. I removed the 10mm bolts which hold the guard plates around the pump and gave it a good clean up.
FollowupID: 311297

Reply By: RLNOMAD - Monday, Mar 08, 2004 at 00:09

Monday, Mar 08, 2004 at 00:09
Had the same thing with mine couple of months ago....3lt 2001...was the sub tank control box gismo ...not in the tank but behind the dash below the radio......was lucky ...warranty job.
AnswerID: 49474

Reply By: Mikef_Patrol - Monday, Mar 08, 2004 at 09:13

Monday, Mar 08, 2004 at 09:13
Hi Matt

Earlier GUs had a problem with the earth on the transfer pump not earthing properly. Check this too.

AnswerID: 49493

Reply By: Member - Raymond - Monday, Mar 08, 2004 at 10:11

Monday, Mar 08, 2004 at 10:11
Hi Matt
I have had the problem on both the 2000 3lt and the 2002 4.2 Nissan. The 3lt was easy to fiux, the computer had got confused and refused to transfer the fuel and the warning light was on.
Simple fix: remove earth lead from battery. If you have a dual battery system remove aux first, then under starting battery. After 20 seconds you will hear a click and then you can connect the earths back up.
If that does not work then it is a replacement of the pump. On my GU 4.2TD the replacement parts are different to what was in the vehicle. Worth chasing Nissan to do it under warrantee.
I am taking out the extended warrantee as one claim pays for it.
AnswerID: 49497

Follow Up By: Ian - Monday, Mar 08, 2004 at 10:17

Monday, Mar 08, 2004 at 10:17
Hi all
wayne is on the right track with the GU fuel transfer problem. My travelling mate had the same problem. Removing the earth leads fromthe batteries resets the computer and the transfer pump will then work.
cheers Ian
FollowupID: 311299

Reply By: basecamp15 - Monday, Mar 08, 2004 at 18:32

Monday, Mar 08, 2004 at 18:32
I just want to clarify what I was talking about to double check if I too have a problem (hope this doesn't constitute a thread hijacking).
My sub tank actually works, I press the button in and it starts delivering fuel to the main tank. When doing this, the green light within the button is on so it's all good.
What I was wondering was should the dash light also be on at this stage or does that only come on when there is a fault? Incidentally the pump does stop when the tank is empty.
The other problem which I don't think is related is the low fuel warning light. It's never worked.
Thanks, Mark.
AnswerID: 49566

Reply By: Member - Errol (York WA) - Monday, Mar 08, 2004 at 18:44

Monday, Mar 08, 2004 at 18:44
Clean the blades on the fuse , that fixed the prob for me . Cheers Matt
AnswerID: 49568

Reply By: Member - Jeffrey - Monday, Mar 08, 2004 at 19:42

Monday, Mar 08, 2004 at 19:42
Hi Matt,
I have a 2000 gu which does the same thing...mine is conflicting with my turbo timer!! what I have to do is remove my neg lead for 24 hours and the computer reset itself then it all works fine until I use my timer again...what a bloody about my drama..I have read all the forum folks ideas and they all sound theisable to me try this and clean the conections. this might just do the trick.
All The Best In Health And Wealth
Jeffrey (AKA JD)
AnswerID: 49583

Reply By: Wayne from the Pilbara - Monday, Mar 08, 2004 at 22:12

Monday, Mar 08, 2004 at 22:12
My 2001 4.2TD GU was doing the same thing.

All it requires is to remove the earth lead as that resets it somehow. Then using a length of wire and two round electrical crimps, make up an earth lead that connects the body to the chassis. Nissan did mine at a ridiculous cost (about $65) because they couldnt tell me exactly what they were doing. I wasn't happy when I saw what they had done, as there was less than $1 worth of parts.

Once that is done, you never have the problem again.

Regarding the pump.. another friend had the pump on their 4.5 petrol die whilst in Perth. Cost approx $700 for the pump. ME??? I'd have paid a bit more, changed the pump system and bought a replacement tank for the tiny 30L. I'm sure that you could install a larger tank that independently feeds the engine rather than the current situation where fuel is transferred to the main tank.

Fix the subtank problem permanently with the earth lead.

Good luck



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AnswerID: 49602

Follow Up By: Roachie - Wednesday, Mar 10, 2004 at 14:53

Wednesday, Mar 10, 2004 at 14:53
Wayne, sorry for being a bit of a dill....but could I ask you:
This lead from the "body to the chassis" you mean the body of the vehicle; or the body of the fuel transfer pump? I'm a bit confused. There are already a number of earth wires to the body/chassis of my GU.
FollowupID: 311583

Follow Up By: Wayne from the Pilbara - Thursday, Mar 11, 2004 at 00:58

Thursday, Mar 11, 2004 at 00:58

The lead that was added by the Nissan dealer basically goes from the front right of the body to the chassis. It attaches behind the headlight onto the body and then runs down and attaches to the chassis near the chassis below. Ah if only I could take a photo for you

I gather that any part of the body (mine is at the front close to where the bonnet opens) down to the chassis will suffice. The wiring is held in place with wire ties and does not look at all well done, but it does work.

The wire is linked between the body of the vehicle to the chassis.

As I said no problems so far. I was really peeved as the transfer couldnt take place and I do LOTS of kilometres when I travel. eg Karratha to Coolgardie overnight. This involved a fill at Newman and then another top up at Meekatharra because the sub tank didnt work.

I hope this helps.




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FollowupID: 311687

Reply By: Member - Matt- Tuesday, Mar 09, 2004 at 00:04

Tuesday, Mar 09, 2004 at 00:04
Thanks to all who shared their advise, I'll give the easy options a crack first and see how it goes, and by the way, the fault did happen at a bad time, following a siesmic track off the road from Paynes Find to Yalgoo... cheers, mat
AnswerID: 49619

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