Sub Tank issue

[jonez911]

hey all i have 2004 gu 3.0l and sub tank is not working pretty sure there isnt even power at the switch. ive been told to hard wire a switch to the pump so i can just manually fill it when i want but want to know if anyone else has this issue.
its not the issue where the light on the dash stays on it just does nothing i can push the button all day long and nothing will happen.

[the evil twin]

When did you notice it stop working?
Is there less than 3/4 fuel in the main?
Have you tried disconnecting the battery?
Have you checked the fuses?

[jonez911]

never worked since i have had it.
yep tryed it at all different fuel levels.
disconnect ed it but not for a length of time.
fuses have all been checked under the steering wheel, is there others?

[the evil twin]

How long have you had the vehicle?
How much fuel is in the sub?
Is the plumbing OK?
Have you physically checked that there is no flow into the main tank filler neck?
When you press the switch in and hold it does the lamp illuminate and go out imediately it is released?

The self test circuit for the sub tank transfer is very comprehensive so it is common to have a false warning light but very unusual to have a real fault that doesn't illuminate the warning light.
Sounds like it may possibly be a fault in the Sub Tank Computer.

[jonez911]

vehicle for about a year.
sub tank is full.
plumbing looks fine to me.
zero flow.
zero illumination of the indicator lights.

thanks for the info so far its really doing my head in now.

[the evil twin]

vehicle for about a year.
sub tank is full.
plumbing looks fine to me.
zero flow.
zero illumination of the indicator lights.

thanks for the info so far its really doing my head in now.

Hmmmm... kind of boils down to likely being one of two things.

Either there is no power at all to the system or the Sub Tank Computer has crapped out.
Also, either of those mean you cannot use the fault code to try and help.
Very outside chance it might be an earthing issue or tank sender but that normally throws a warning light.

Does the orange "Sub Tank" warning light illuminate with the other dash warnings when you switch the ign on?

I haven't got a copy of the circuit with me ATM so I am working from memory.
If Rodney spots the thread he may have an idea for something I haven't thought of.

[Rocket55]

Do you have poor radio reception?
Central locking doesn't work consistently?
Have you got spot lights or winch mounted on the front and earthed to the bullbar? This will then run the earth current through the sub tank wiring.

Try putting a solid earth between the body and the chassis ($12) from Supercrap or Whittworths etc. and see if that fixes it

[MEGOMONSTER]

My ARB says the they commonly replace switches on sub tanks.

[Yendor]

If the light in the sub tank switch doesn't light up when it's depressed, I would start by checking that the sub tank switch and sub tank computer still have their electrical plugs connected.

[Yendor]

My ARB says the they commonly replace switches on sub tanks.

The switch in the dash or the sender unit in the sub tank?

[the evil twin]

If the light in the sub tank switch doesn't light up when it's depressed, I would start by checking that the sub tank switch and sub tank computer still have their electrical plugs connected.

Hiya Rodney,

No continuity to the switch should normally show a warning light but after that then a power issue is about all it could be eh... and that was what was driving my earlier Q's.

I was wondering if there is a fault and the prev owner pulled a plug or whatever to make the warning light go away when they were selling?

[boots]

There is also a fuse under the bonnet RHS for the sub tank. Worth a look.

[Yendor]

Hiya Rodney,

No continuity to the switch should normally show a warning light but after that then a power issue is about all it could be eh... and that was what was driving my earlier Q's.

I was wondering if there is a fault and the prev owner pulled a plug or whatever to make the warning light go away when they were selling?


Hey mate,

I could see where you were going with your questions and I agree with you. You had it covered.

Based on that and what the OP stated I started to go deeper. If the sub tank switch was disconnected and the rest of the circuit was working correctly, yes I would expect the warning light in the dash to come on when the ignition was turned on and go off once the engine was running.

If the sub tank control unit was disconnected then I would expect both the warning light in the switch and the dash not to work.

I only mentioned the switch because you basically have to remove the switch to get to the control unit.

I don't think it's a power supply problem because there would also be issues with other warning lights. It also doesn't sound like an earth problem.

It comes down to how much diagnostic work the OP wants to put in. Based on his first post he's happy just to fit an aftermarket switch in the dash and hopefully remembers to turn it off before the pump runs dry and that's fine.

Slightly off topic did you end up fitting an aftermarket pump to yours?.

Cheers Rodney

[the evil twin]

snip...

Slightly off topic did you end up fitting an aftermarket pump to yours?.

Cheers Rodney

In the end sheer bloody mindedness wouldn't let me admit defeat so I perservered and fixed the factory system.

It was the old two faults at once gotcha... when I got the power sorted it let me see the fault codes which told me the main tank 'not full' switch was open circuit and that was a broken wire inside the tank on the sender unit.

[MEGOMONSTER]

The switch in the dash or the sender unit in the sub tank?

Switch in the dash, ARB HOPPERS carry new genuine switches in stock

[jonez911]

thanks guys for all the replies. ill try do somemore seaching tonight and see what i come up with i might even run 12v straigh to the pump to make sure that works, ill test the switch buy just pluggin it into the dimister (pending on switch config).
i didnt know about the fuse under the hood so ill check that also.

[Yendor]

In the end sheer bloody mindedness wouldn't let me admit defeat so I perservered and fixed the factory system.

It was the old two faults at once gotcha... when I got the power sorted it let me see the fault codes which told me the main tank 'not full' switch was open circuit and that was a broken wire inside the tank on the sender unit.

lol….Those two fault problems are always a PITA.

[Yendor]

Switch in the dash, ARB HOPPERS carry new genuine switches in stock

Thanks mate, it's always interesting to know what faults other people are coming across.

[jonez911]

ok so i think i need to wire in a new switch. does anyone have a wiring diagram of this subtank system?
or a how to wire in a manual switch?