Sub Tank Switch by pass

[Rick111]

Yes I know, ther is plenty of threads on this issue, however I can't seem to find anything that shows you how to put a manual switch in to by-pass the subtank controller. If anbyone has done this could you please put up a wiring diagram to show what you did.

I don't know if this can be done, but what I would like to do is keep original pump & sub tank switch in place, somehow wire the switch direct to 12v power from somewhere else other than the sub tank controller, this way the controller is elliminated & stick some black tape over the light on the dash as it's too much work to pull the dash out to remove the globe.

The only issue with this mod is you must remember not to overfill the main tank & don't forget to turn off the pump so it doesn't run dry.

[MudRunnerTD]

I am not sure I understand why? What are you trying to achieve. ??

A little confused?

[TimE]

I had to do that in the Simpson when the FULL after market 80l subtank broke its rear mounting brackets, dropped to the track and was held on by the front mounts, it pulled out the wireing loom. Just ran a wire straight from the + of the battery to an alligator clip on a small screw driver which was touched to the pump to pump fuel into the main tank prior to removing the sub tank.

Could have run the wire through a switch with the appropriate connector directly onto the pump, but as asked above, short of my catastrophic issue, why would you want to do it?

[Evo]

Yes I know, ther is plenty of threads on this issue, however I can't seem to find anything that shows you how to put a manual switch in to by-pass the subtank controller. If anbyone has done this could you please put up a wiring diagram to show what you did.

I don't know if this can be done, but what I would like to do is keep original pump & sub tank switch in place, somehow wire the switch direct to 12v power from somewhere else other than the sub tank controller, this way the controller is elliminated & stick some black tape over the light on the dash as it's too much work to pull the dash out to remove the globe.

The only issue with this mod is you must remember not to overfill the main tank & don't forget to turn off the pump so it doesn't run dry.

It's only a 5 min or less job to take the globe out.

Evo

[Rick111]

Due to the sub tank light comming on, the fuel will not transfer to the main tank, so what I want to do is use the existing pump & sub tank switch py-pass the sub tank controller & get power from somewhere else to power the pump thus totally eliminating the sub tank controller system. Basically all I need to know is where to get power from & can I use the existing sub tank switch.

[MudRunnerTD]

Due to the sub tank light comming on, the fuel will not transfer to the main tank, so what I want to do is use the existing pump & sub tank switch py-pass the sub tank controller & get power from somewhere else to power the pump thus totally eliminating the sub tank controller system. Basically all I need to know is where to get power from & can I use the existing sub tank switch.

have you tested the Switch? assuming that you are eliminating the loom because you think the fault if there? You can take the power from the Cig Lighter. I am a little concerned though that your plan results in all the mechanical parts in the loop (Switch, Pump, Sender, Relay) being retained because they are all ok and the fault is in the wiring?? I'd be way more inclined to be checking for a fault in the mechanical side of the circuit rather than the actual wire.

Sorry not having a go mate, just trying to help with limited info from you.

Are you absolutely certain that there is a fault? Silly question i know. There has been quite a bit written of late on this subject. The light on the dash does not light up in my GUIV when transferring but does on other members? Odd. The transfer is very very very slow. 20 to 30mins to empty the tank. I always start my transfer when the fuel light comes on in the GUIV and it can take 10minutes to pump enough to drop the fuel light off again!

[threedogs]

you can hardly notice my sub light switch day or night, as you
suggested why not tape over half of the light so its not so annoying
if that's your aim, I'm confused a bit too , but that's not hard theses days LOl

[Ian2011]

I too wish to rewire this circuit, I am now having the same issue as numerous people have brought up about the Sub tank light remaining on all of the time. I have done the "remove power from battery" numerous times in my trip from Wodonga to Darwin to try and utilise both tanks but it's getting a bit ridicules doing this on almost a daily basis. Has anyone actually solved this problem yet, reading all of the other threads on this topic has not given any info other then cleaning terminals, disconnecting the battery or fitting an additional earth strap. What is the purpose of the sub tank controller behind the radio, if the tank has to be manually transferred anyway, why would it need a controller apart from pumping some fuel between tanks on start up, can this be removed from the circuit to provide a direct link to the transfer pump whilst using the existing switch.

Has anyone actually done this modification or even come close to solving this issue.

[the evil twin]

The controller serves a few purposes, the main two being...

It won't let you overfill the main tank if there is more fuel in the sub than space in the main.
and
It tests that the pump will actually work when you select it.

No major drama in bypassing it all with a switch to 12 volts.
However the only way to check if the pump actually transfers is to monitor the sub gauge is dropping or pop the cap off the main filler and see if the fuel is flowing and you also need to make sure you have enough tankage to accept the sub tank fuel.

[Ian2011]

There is no problem with the pump, when it is reset after the battery is disconnected, it works as it is supposed to. I generally only transferred sub tank fuel to main at half empty on the main so there would be enough room based on my existing habits. Ideally I would like to leave it all as is if, someone could give a definitive answer on what causes the light to stay on in the first place. Maybe I might dedicate some real time to the issue and attempt to sort it out.

[Rumcajs]

Here ya go ==>

[Ian2011]

Thanks for that Rumcajs, guess I have to try to find my fault now, these diagrams will go a long way to help.

[Ian2011]

Don't suppose you have the diagnostic procedures to check the fault codes.

[Rumcajs]

Don't suppose you have the diagnostic procedures to check the fault codes.

Now who is pushing some luck, LOL
here ==>

[Yendor]

I too wish to rewire this circuit, I am now having the same issue as numerous people have brought up about the Sub tank light remaining on all of the time. I have done the "remove power from battery" numerous times in my trip from Wodonga to Darwin to try and utilise both tanks but it's getting a bit ridicules doing this on almost a daily basis. Has anyone actually solved this problem yet, reading all of the other threads on this topic has not given any info other then cleaning terminals, disconnecting the battery or fitting an additional earth strap. What is the purpose of the sub tank controller behind the radio, if the tank has to be manually transferred anyway, why would it need a controller apart from pumping some fuel between tanks on start up, can this be removed from the circuit to provide a direct link to the transfer pump whilst using the existing switch.

Has anyone actually done this modification or even come close to solving this issue.

Have you installed an earth strap to the chassis?

You can wire a simple on/off switch to run the fuel transfer pump if you like.

The controller is to make sure you don't overfill the main tank and that fuel transfer stops when the sub tank is empty so you don't run the fuel pump dry.

Do you still have standard fuel tanks or long range tanks fitted?

[Ian2011]

I haven't actually put an earth strap on, was more interested in actually discovering what caused the problems rather then just putting a 'fix' on. In saying that I have not had the light come on for three days since I stopped letting the turbo timer switch the car off. Running a simple on/off switch, that's what the switch on the dash is anyway, so to run another without solving the issue seems pointless unless I remove the controller.

[Yendor]

I haven't actually put an earth strap on, was more interested in actually discovering what caused the problems rather then just putting a 'fix' on. In saying that I have not had the light come on for three days since I stopped letting the turbo timer switch the car off. Running a simple on/off switch, that's what the switch on the dash is anyway, so to run another without solving the issue seems pointless unless I remove the controller.

The chassis is not earthed from factory. Nissan wiring (including earth circuits) is only just satisfactory for a standard vehicle. Once you start modifying it, adding extra electrical accessories and the wiring starts getting old this can cause all sorts of electrical problems. One "fix" is to add an earth strap between the body and chassis. This has even been recommended by Nissan. For something that cost so little to do I find it strange that you don't want to do it.

Another known cause of fuel transfer electrical problems is the shut down timer. If the incorrect one has been installed this will bring on the sub tank light.

The original fuel transfer switch is not an on/off switch it is a momentary switch. When the switch is pressed it sends a signal to the sub tank control unit. Then if the control unit sees all the correct information from the sensors in both fuel tanks it will switch on the fuel pump. I think the control unit also measures the power the fuel transfer pump is using and if this is out of spec or any of the other sensors are out of spec the control unit stops the fuel transfer and brings on the light.

In your other post you said "I too wish to rewire this circuit". The easiest way to do this is to fit an on/off switch in the dash to switch a relay on and off that turns the fuel pump on and off. Then just remember to switch the pump off because the biggest killer of pumps is to run them dry.

[gaddy]

The chassis is not earthed from factory. Nissan wiring (including earth circuits) is only just satisfactory for a standard vehicle. Once you start modifying it, adding extra electrical accessories and the wiring starts getting old this can cause all sorts of electrical problems. One "fix" is to add an earth strap between the body and chassis. This has even been recommended by Nissan. For something that cost so little to do I find it strange that you don't want to do .

Hey rod is this just an extension of the body earth to the chassis , I'm not having any issues but it is s simple thing and I prefer prevention over a future falt . Sorry for the high jack

Steve

[Yendor]

Hey rod is this just an extension of the body earth to the chassis , I'm not having any issues but it is s simple thing and I prefer prevention over a future falt . Sorry for the high jack

Steve

That will work fine.

Most people connect the earth from the body to the chassis near the fuel tanks.

This is what Nissan recommended.

[gaddy]

Thanks , simple as

Steve