Sub Tank not working

[mickw1912]

GU 42, 05 model, just knocked the NATS off the back of the fuel pump, and now I have no Sub tank. The pump worked fine pre NATS issue, but it wouldn't transfer during the NATS problem ie; while the security dash light was on in a solid state. I disconnected the battery to see if that would reset it.
Im considering an auto Elec to do a bipass, but does anyone know an easier fix.

Regards Mick.

[Touses]

Hello again. Over in the auto elec forum there is a thread a few days back titled sub tank issues.

Check that out it may have your answers.

[MudRunnerTD]

Hello again. Over in the auto elec forum there is a thread a few days back titled sub tank issues.

Check that out it may have your answers.

http://www.nissanpatrol.com.au/forums/showthread.php?37272-Sub-tank-issues

[Yendor]

GU 42, 05 model, just knocked the NATS off the back of the fuel pump, and now I have no Sub tank. The pump worked fine pre NATS issue, but it wouldn't transfer during the NATS problem ie; while the security dash light was on in a solid state. I disconnected the battery to see if that would reset it.
Im considering an auto Elec to do a bipass, but does anyone know an easier fix.

Regards Mick.

NATS shouldn't have any affect on the sub tank.

Do both fuel gauges work correctly?. Does the light in the sub tank switch come on when pressed?, Does the warning light come on in the dash?.

Do you have an engine shut down timer fitted?

How long ago did you fit the Sony head unit? Did you reconnect the sub tank switch? Does the sub tank switch light up when the headlights are turned on?

If you really want to bypass it, you can just use an on/off switch but you will need to remember to switch it off before the pump runs dry.

[mickw1912]

Hi Yendor,

So both tanks gauges appear to be working properly on the dash, and the sub light is illuminated with the full tank.

The sub switch lights up when the head lights are turned on.

I do have a timer fitted.

The Sony unit was in the car when I got it, and all has been working well.

[Yendor]

Hi Yendor,

So both tanks gauges appear to be working properly on the dash, and the sub light is illuminated with the full tank.

The sub switch lights up when the head lights are turned on.

I do have a timer fitted.

The Sony unit was in the car when I got it, and all has been working well.

If the main tank is above a 2/3 full, fuel will not transfer.

[mickw1912]

Tried when it was 1/3, 1st time I realized it didn't pump.

[Yendor]

Check for power and earth at the transfer pump.

[Yendor]

Hi Yendor,

So both tanks gauges appear to be working properly on the dash, and the sub light is illuminated with the full tank.

The sub switch lights up when the head lights are turned on.

I do have a timer fitted.

The Sony unit was in the car when I got it, and all has been working well.

Which light? The light in the switch or the light in the dash? Does it only light up when the main tank is full?

[mickw1912]

Which light? The light in the switch or the light in the dash? Does it only light up when the main tank is full?

The "sub" dash is illuminated, and the back lighting of the switch, when dash lights up. There's no transfer light at all.

[the evil twin]

The "sub" dash is illuminated, and the back lighting of the switch, when dash lights up. There's no transfer light at all.

The 'transfer' light in the switch won't illuminate while the 'sub tank' fail light in the dash is on.
You need to reset the sub tank computer by either, disconnecting the battery, pulling the fuses or disconnecting the computer.
Next time you turn the ign on the 'sub tank' light will go out and the computer will then do a self check (takes a minute or so).
If there is no fault teh light will stay off and all will work as advertised.
If there is still a fault the 'sub tank' light will come back on.

If the light comes back on you can either work thru the tests in the manual or get the computer to show the fault codes, again, by following the manual.
It can be, pump, switch computer, sub tank sender, main tank sender or wiring

[mickw1912]

The 'transfer' light in the switch won't illuminate while the 'sub tank' fail light in the dash is on.
You need to reset the sub tank computer by either, disconnecting the battery, pulling the fuses or disconnecting the computer.
Next time you turn the ign on the 'sub tank' light will go out and the computer will then do a self check (takes a minute or so).
If there is no fault teh light will stay off and all will work as advertised.
If there is still a fault the 'sub tank' light will come back on.

If the light comes back on you can either work thru the tests in the manual or get the computer to show the fault codes, again, by following the manual.
It can be, pump, switch computer, sub tank sender, main tank sender or wiring

I did disconnect the positive terminal on the battery for 30+ mins, but no change. I'll start testing this weekend and post any results.

[Yendor]

I did disconnect the positive terminal on the battery for 30+ mins, but no change. I'll start testing this weekend and post any results.

So the sub tank warning light in the dash was on after disconnecting the battery? even before pushing the sub tank transfer switch?

[mickw1912]

So the sub tank warning light in the dash was on after disconnecting the battery? even before pushing the sub tank transfer switch?

Thats correct mate.

[Yendor]

Thats correct mate.

Try running a new earth lead between the negative battery terminal and the chassis ( or between the body and chassis) it doesn't matter which one as long as one end is connected to the chassis.

Then try resetting the computer again, this time by unplugging it for half an hour. It's located under the radio on the LHS.

[mickw1912]

Try running a new earth lead between the negative battery terminal and the chassis ( or between the body and chassis) it doesn't matter which one as long as one end is connected to the chassis.

Then try resetting the computer again, this time by unplugging it for half an hour. It's located under the radio on the LHS.

So Yendor, disconnecting the battery should affectedly do that to the system, shouldnt it?

Well, I went back out in the dark just now to disconnect the battery again. What i found was the red arc SBI12 dual battery solenoid was still glowing on top, that meant the second battery was still connected and powering the the mains cables.

This time I took both off, and has reset itself. The dash 'sub tank' has gone out.

Rooky Error right there.....

[Yendor]

So Yendor, disconnecting the battery should affectedly do that to the system, shouldnt it?

Well, I went back out in the dark just now to disconnect the battery again. What i found was the red arc SBI12 dual battery solenoid was still glowing on top, that meant the second battery was still connected and powering the the mains cables.

This time I took both off, and has reset itself. The dash 'sub tank' has gone out.

Rooky Error right there.....

Some aftermarket electronic units can hold a charge when disconnected from the main battery. Disconnecting the sub tank ECU eliminates all other electronics in the vehicle from maintaing the memory in the sub tank ECU.

Disconnecting the battery has not fixed your problem. It's like when you reboot a computer after it crashes. You have just reset the sub tank ECU. If the problem is still present the dash light will come on again.

As I have said, start by adding the extra earth to the chassis. This is a common problem with GU's and hopefully it will fix your problem.

[the evil twin]

When I get a fail light I pull the fuse or the computer plug rather than dick around with Battery terminals.
I get one about once a year or so because I am running a different transfer pump than factory and every now and then the 'poota figures it out and trips a fail.

Do what Rodney said and put in a chassis to body earth even if the light does not come back on again.
Dodgy earths cause all sorts of issues than just the sub tank faults in a Trol

[mickw1912]

Guys, I took out both batteries, so no power what so ever. It reset the system and I now have a sub tank once again.
Thanks for all help once again.