Sub tank issues

[Viiper]

As one of the most iconic problems seen in patrols, 30% of users get that nasty sub tank problem.
Unfortunately, so have I. I've looked at solutions many of which say that disconnecting the battery for an hour to overnight can fix the problem, has anyone here had this problem and know of any solutions for it?

Cheers -Viiper

[mudski]

You haven't mentioned the actual issue your having...

[my third 256]

earth strap could be the problem

[Nightjar]

What problem????

[threedogs]

Problem was he got his manual,,, shame really, more info here than a manual

[Clunk]

Problem was he got his manual,,, shame really, more info here than a manual
A wee bit pessimistic there TD

[threedogs]

Bit keen you think, we'll see I have a feeling lol

[Viiper]

Hmm, I guess I didn't make myself quite clear. By the way, with the manual... I thought it would've been a car manual, but I had a little look through and it's basically a workshop manual (I already have a gregory one)
But my problem with the sub fuel tank is the light comes on and stays on, it's about 3 quarters full and the main tank is only a quarter full, it will not transfer the sub tanks fuel to the main tank and the light on the dash just stays there, no matter how much I press that damn button. It just won't go away, I'm having a feeling that i'm going to need to unplug the fuel module for an hour or two and plug it back in (which I haven't done yet) I've unplugged the battery completely for about 12 hours and that didn't seem to have an effect on it. It went away for a couple of minutes but came back. So besides the battery trick, anyone have any clue?

[Clunk]

some folk have had a bit of success with adding an extra earth strap but whether that will help with your problem I cant say

[threedogs]

ET is your go to man for this, good to see you back my bad lol
Patrols are rotten for poor earth straps,
but your problem sounds more about switching

[the evil twin]

Hmm, I guess I didn't make myself quite clear. By the way, with the manual... I thought it would've been a car manual, but I had a little look through and it's basically a workshop manual (I already have a gregory one)
But my problem with the sub fuel tank is the light comes on and stays on, it's about 3 quarters full and the main tank is only a quarter full, it will not transfer the sub tanks fuel to the main tank and the light on the dash just stays there, no matter how much I press that damn button. It just won't go away, I'm having a feeling that i'm going to need to unplug the fuel module for an hour or two and plug it back in (which I haven't done yet) I've unplugged the battery completely for about 12 hours and that didn't seem to have an effect on it. It went away for a couple of minutes but came back. So besides the battery trick, anyone have any clue?

The Sub Tank Warning Light is a 'latching' fault IE even if the fault goes away the light stays on.

When the Warning Light is on all fuel transfer is inhibited, no matter how hard or how often you press the transfer button

Disconnecting the battery resets the Fault Detection and extinguishes the light.
So does pulling the fuses or disconnecting the computer module.

The very next time you turn the ignition on the Sub Tank Computer does a self test and if it thinks there is a fault you are back at square one.
This takes about a minute depending... that is why the light came back on after you had disconnected the Battery (no matter how long).

The Manual will tell you how to get the fault code for what the computer thinks is faulty and you can fault find from there.
It can be the Main Tank Sender, Aux Tank Sender, Transfer Switch, Fuel Pump or wiring so the code will help heaps.

A random fix that works some of the time is additional earthing from the chassis to the body to the battery -ve

[MudRunnerTD]

I had the SubTank light come on for the first time since owning the GUIV in 7 years over the weekend. It does not function while transferring and only appears during Ignition sequence. I was out of reception to check the forum. I pulled the fuse to the subtank and it was fine. I was going to fault find it this week. It turns out my Negative terminal on the cranking battery was knackered and the whole car went dead when i parked it last night. I did a mod to the terminal this morning and the car started first kick and the light was gone. For Sure it was a dodgy Earth. The Nissan terminal is rubbish. Swap it out, it might help.

[MudRunnerTD]

Hmm, I guess I didn't make myself quite clear. By the way, with the manual... I thought it would've been a car manual, but I had a little look through and it's basically a workshop manual (I already have a gregory one)


lol and your 200page Gregorys is an abridged version of the real thing. The 1200 page Workshop Manual you now have on your computer, your iPad and your Phone is uncomparable. but stick with your Gregorys if you like.

[Viiper]

The Sub Tank Warning Light is a 'latching' fault IE even if the fault goes away the light stays on.

When the Warning Light is on all fuel transfer is inhibited, no matter how hard or how often you press the transfer button

Disconnecting the battery resets the Fault Detection and extinguishes the light.
So does pulling the fuses or disconnecting the computer module.

The very next time you turn the ignition on the Sub Tank Computer does a self test and if it thinks there is a fault you are back at square one.
This takes about a minute depending... that is why the light came back on after you had disconnected the Battery (no matter how long).

The Manual will tell you how to get the fault code for what the computer thinks is faulty and you can fault find from there.
It can be the Main Tank Sender, Aux Tank Sender, Transfer Switch, Fuel Pump or wiring so the code will help heaps.

A random fix that works some of the time is additional earthing from the chassis to the body to the battery -ve

The light on the switch itself (not the dash) Does not come on at all. Could it be the switch/wiring or still what you said?

[Bigcol]

from my understanding,
if the Fuel Transfer system thinks there is a problem (and the DASH light stays on) you will not get any power to the switch, hence no light on

if you can get the fault code (scan gauge / OBDII / mechanic) you will then know in what area to look
could be the switch itself
could be the fuel transfer pump
could be the fuel transfer controller
could be the fuel gauge
could be the main tank
could be because its a bad earth
could be a broken wire to the Aux tank
could be a lovely day to go to the beach..............................

[the evil twin]

The light on the switch itself (not the dash) Does not come on at all. Could it be the switch/wiring or still what you said?

Is the dash warning light on?

If yes, then the switch light will not come on

If no, (and fuel is transferring, you can check by looking in the main tank filler) then the dinky little globe in the switch is probably blown.

[Viiper]

Is the dash warning light on?

If yes, then the switch light will not come on

If no, (and fuel is transferring, you can check by looking in the main tank filler) then the dinky little globe in the switch is probably blown.

I actually went and did some testing just now, I disconnected the battery for about 5 minutes, connected it, the subtank light on the dash wasn't on, I hit the switch. Switch light came on, left it for a couple of seconds, hit the switch again and the light went off, then the dash light came back and and as you and bigcol said, doesn't do a thing while the dash light is on...

[the evil twin]

That is the self test proggy doing it's thing.
It thinks there is a fault in the Sub Tank Control system.
It will now stay like that until you fix the fault AND disconnect power again
You can either disco the battery or pull the fuse, either will reset it.

[Viiper]

Haha, you're all going to get a kick out of this...

So when the evil twin said: "You can either disco the battery or pull the fuse, either will reset it."
Something in me clicked, I didn't actually go and check the fuse box... So I went today and had a look, blown fuse lmao... All good now, transfer rate is slow as a donkey, but I've been told that's how it's mean't to be so it stops diesel foaming or some nonsense in that manner.

So my tip to anyone who is having this problem, make sure you check your sub tank fuse to see if it is blown.

[the evil twin]

ROFL... well, at least you got it going.

Transfer rate on the factory pump is 1 an 1/2 LPM nominal so a 30 litre Wagon sub should empty in about 20 mins.

But... there is always a but... you will only have a full Sub on rare occasions as the 'self test' will pump up to a 1/2 litre every time you start the vehicle.
This can lead to people getting very good mileage around town if they run on the main only and aren't wise to the issue

[Viiper]

Would you have any clue as to what this switch is?
62880

[the evil twin]

Thats where the Hand Throttle is on mine... and that is an aftermarket switch.

Maybe someone just used it as a convenient spot to mount a switch for an accessory at some stage

[King_ady1]

Have u pressed it yet?? I don't have anything in that position in mine so it's possibly just a convenient spot for something like et said.