Subtank problem

[syednaimath]

Hi all,
My car details:
Nissan Patrol Super Safari 2006 Petrol engine 4800 Automatic transmission
Problem:
Sub Tank Indicator remains on always
Light on Sub Tank switch when pressed does not glow

Tried the following:
1. Disconnected battery for a while and connected back. Sub Tank Indicator went off after sometime again returned back.
2. Opened A/C and heater panel. unplugged Sub Tank control unit and plugged it back. Sub Tank Indicator went off next day morning again returned back.

At this point I am suspecting Sub Tank switch. Please let me know whether changing this switch will do or I have to check something else.

Thanks in Advance
Regards
Syed

[JG Shields]

Syed,

The sub-tank light does not only indicate to a sub-tank problem. Refer to the manuals to see what other probable faults are linked to the sub-tank indicator light. It also differ between models. For starters, I will also have a close look at an alternator (charge and/or regulator) problem, ground/earth problems or a relay on the electrical system somewhere. With the limited info available, my gutt tells me this is not a sub-tank system problem.

[syednaimath]

JG,

Thanks alot for your reply..i will do that this weekend..

[Sias]

I have the same problem after installing the long range tank! I've checked the fuses and have crawled under the car to check for loose wiring but found nothing wrong.
The car is in today for the new dash and I asked them to have a look.
Another problem I have is that the fan is stuck on the "demist/footwell" position and does not want to go to the "face" vents. Any suggestions on how to get it unstuck? Moving the dial from "face" to "feet" a 1000000 times does not help...

[Margo]

Hi Guys.... Has anyone found a solution to the Subtank Problem?

I filled my two tanks this morning and after the filling, my subtank warning light came on, on the dash.... Any ideas of what to do?

Ive switched on, off, played with all the buttons. Opened and closed the caps, etc... :( Nothing!. Light still burns away

, please.

Thanks.

Margo

[Herrie]

To make sure my sub-tank work properly I keep it full and every second time I go to fill up, I empty the sub-tank into the main-tank. Up to now I never had a problem. If you leave the sub-tank empty and don't use it regularly, you will pick up problems.

I will check my manual and let you know.

[Herrie]

This is what the manual says:

Sub Fuel Tank Control System Operation
This system controls the sub fuel pump operation based on the signals sent from the full switch (main fuel
tank), the empty switch (sub fuel tank) and the sub fuel tank switch.
The full switch is built into the main fuel tank. It senses the main fuel tank fuel level. When the specified level
is exceeded, the full switch operates to suspend sub fuel pump operation, preventing excess fuel from flowing
into the main fuel tank.
The empty switch is located inside the sub fuel tank. It senses the sub fuel tank fuel level. When fuel in the
sub fuel tank drops below the specified level, the empty switch operates to suspend sub fuel pump operation.
If the sub fuel pump stop conditions are not met after the sub fuel pump has been operated for 1 hour, the
sub fuel pump automatically stops.

If the system becomes inoperative, the sub fuel tank control system
function will be suspended.
The fail-safe system function will then activate, illuminating the sub
fuel tank warning lamp.
I The sub fuel tank warning lamp will light up when the ignition
switch is turned ON without the engine running. This is to check
the blown lamp.

[Margo]

Hi, Thanks for the reply. Hope you did a copy and paste and not a retype of everything?
I really have no idea what I should be doing right now. I use my subtank all the time, the fuel in there doesn't last to long anyway? So basically when main tank is on a quarter, i empty the sub into main, drive about 200km's (if that) and then full both up again. Am I doing it wrong??

But now this problem of the light on the dash board, its not the light that tells you have no petrol left, its the actual warning light. I dont understand or know what is wrong. I really hope the petrol attendent didnt do something to it while i was not looking, he was oh so interested in the fact that there were two inlets... So very inquisitive... Which really freaks me out a bit, hope he didnt prod and poke at the tanks.. :(

Should i have someone at work disconnect my battery for me tomorrow and see what it does?

[JG Shields]

Margo, it seems as if your sub-tank still pumps the petrol to the main tank, irrespective of the "light" issue. right? If this is true, it may be that the sub-tank light has got nothing to do with the sub-tank itself. Nissan uses various lights with different flashing patterns to indicate to different faults. I once lost an alternator along the road. The first light that came on was the sub-tank light. I ignored the light until my alternator packed-up completely. I learned afterwards that the sub-tank light indicated to a shortage of current in some other area of the electronics, hence the light.

My suggestion would be to have your alternator tested as weel as your electrical wiring ground couplings.

[Margo]

Hi JG...

No, it does not pump...The button that you push to allow for the petrol to be pumped into main tank, does not even want to work :( SO i have NO idea.. ARGH THis car is driving me up the wall.