Find a home for these wires please

[57flw]

I am working on a friends 2000 GU2 petrol Patrol.
Sub tank light is on and the transfer of fuel does not happen.
There is two wires, Green and Grey-perhaps Black (as shown in the photo) that I cannot find a home for.
They are at the rear of the sub tank and in front of the rear diff.
Can someone assist please.
Ken

[Trolling82]

Not sure but the other gray you have what that for mine is not connected


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[Lieney]

Maybe something to do with the pump in the sub tank. (wires loose, pump not pumping, lights on but nothings happening: I know people like that)
Check fuse panel to ensure fuse hasn't blown (if there is one) for the sub tank pump or related circuit.
Check to see if there is any voltage at either wire when light is on, or the switch is pushed.
If there is voltage then I'd say it should be connected to the pump.
Is the pump connected?

[Yendor]

What colour are the wires?

The early GUs had a problem with a poor earth to the chassis, this would often cause the fuel transfer module to lock up.

The fix was to run a new earth lead from the chassis to the body or negative battery post.

You will need to also disconnect the battery for about 30 minutes to reset the transfer module. If disconnecting the battery does not reset it, you will need to unplug the fuel transfer module for 30 minutes.

[57flw]

Thanks for the reply.
The wires are Green and Grey-perhaps Black(hard to see with the surrounding tubing.
I have carried out a good clean on all the battery leads and I have read about the need for a decent earth from the chassis to the body, on this forum.
My immediate problem is finding out where the two wires go. There is not much length to play with so I am a little lost at the moment.
I am not experienced on this vehicle so do not know what part is what or what it does.
To allow me to follow your suggestion of unplugging the fuel transfer module for 30 minutes I would need to be told where it is located.
I have asked the owner to provide me with a workshop manual.

[MC97GQ]

Mate,

Have you put a test light/multimeter on the wires to see if they are live, or could be live.

If you have someone to help, maybe test the wires for continuity by having your offsider switch things on and off until you find out what they could do.

Anyway mate you have Yendor on the case and he's pretty cluey about this sort of thing.

Good luck with it

Mark

[the evil twin]

As posted by others, run an auxiliary earth from the tank then disconnect the battery for at least 30 minutes and try the transfer system again. If it doesn't reset then get stuck into the fault finding

[Robo]

Why not look at vehicle wiring diagrams.
see what wires have a plug in that location.
you should be able to find wire colours info etc, to also narrow your search
any thing to do with the fuel tank system,senders sounds like first place to check.
cheers

[Yendor]

Thanks for the reply.
The wires are Green and Grey-perhaps Black(hard to see with the surrounding tubing.
I have carried out a good clean on all the battery leads and I have read about the need for a decent earth from the chassis to the body, on this forum.
My immediate problem is finding out where the two wires go. There is not much length to play with so I am a little lost at the moment.
I am not experienced on this vehicle so do not know what part is what or what it does.
To allow me to follow your suggestion of unplugging the fuel transfer module for 30 minutes I would need to be told where it is located.
I have asked the owner to provide me with a workshop manual.

If the wire is Green and the other one is Black they will be for the factory diff lock, if fitted.

If the vehicle doesn't have a factory diff lock fitted the harness is normally tied back on it's self. I would say it's come loose and got caught up in the tail shaft.

Just tape then up individually and tie it up out of the way.

You will need to run an earth to the chassis.

I would try disconnecting the battery first, it's the easiest way and normally is enough to reset it.

The fuel transfer module is located in the dash below the radio on the LHS, if needed I can post a picture showing it's rough location from the workshop manual.

[57flw]

Yendor,
Thanks for your help. Here's where I am up to.
Finished the brake job which was the original main task.
The other two jobs are sub tank not working and flat battery with the charge light showing on the dash.
Charged the battery and tested it. 11.9v engine off. Started the engine, still 11.9volts. Removed alternator and the auto elec confirmed my test. New alternator for $250 on it's way.

Pulled the sub tank switch out, stripped it and cleaned all the contacts. Looks fine. Is there any tests I can carry out whilst the switch is out?

Getting back to my two wires, or I should say the young Lady's wires who owns the vehicle, there is no power to them and the vehicle does not have a diff lock. As you stated perhaps they are part of the loom just in case. If nothing else shows up I will just tape and secure them out of the way.

I will need to wait until the new alternator arrives before I can reconnect the battery and see if the dash sub light is still activated.

How can I test to see if the sub tank pump works?

Regards
Ken

[the evil twin]

Yendor,
Thanks for your help. Here's where I am up to.
Finished the brake job which was the original main task.
The other two jobs are sub tank not working and flat battery with the charge light showing on the dash.
Charged the battery and tested it. 11.9v engine off. Started the engine, still 11.9volts. Removed alternator and the auto elec confirmed my test. New alternator for $250 on it's way.

Pulled the sub tank switch out, stripped it and cleaned all the contacts. Looks fine. Is there any tests I can carry out whilst the switch is out?

Getting back to my two wires, or I should say the young Lady's wires who owns the vehicle, there is no power to them and the vehicle does not have a diff lock. As you stated perhaps they are part of the loom just in case. If nothing else shows up I will just tape and secure them out of the way.

I will need to wait until the new alternator arrives before I can reconnect the battery and see if the dash sub light is still activated.

How can I test to see if the sub tank pump works?

Regards
Ken

Hold the bus dude... the busted Alternator makes a big difference to your problem.... you only told us half the story before...

Sub tank light etc are classic symptoms of the faulty alternator. Heaps of threads on here about that.

Wait until you get the new Alternator fitted and the sub tank transfer problem will 99 times out of 100 disappear

[57flw]

Sorry about that.
I usually try and supply all the facts before asking anything.
The lady who owns the vehicle purchased it about three months ago and she said the sub tank has never worked for her. I could not imagine she has had an alternator problem all that time as well.
As I said in my last post I will need to wait until the new alternator arrives before I can reconnect the battery and see if the dash sub light is still activated.
I will wait in anticipation and hope that when I fit the alternator the sub tank light will go off and the transfer pump will work.

Many thanks for your experience and input.
Ken

[Yendor]

Hi Ken,

The sub tank switch is basically an on/off switch. I will post the wiring diagram for the switch so you can check the operation of the contacts in the switch (February 2000 onwards).

The best way to check if the sub tank is transferring fuel into the main tank. Is to remove the main fuel filler cap and look down the filler neck.

If the pump is working you will see the fuel being pumped in.

The main fuel tank has to be below 3/4 full and the engine running.

Cheers Rodney

[the evil twin]

Sorry about that.
I usually try and supply all the facts before asking anything.
The lady who owns the vehicle purchased it about three months ago and she said the sub tank has never worked for her. I could not imagine she has had an alternator problem all that time as well.
As I said in my last post I will need to wait until the new alternator arrives before I can reconnect the battery and see if the dash sub light is still activated.
I will wait in anticipation and hope that when I fit the alternator the sub tank light will go off and the transfer pump will work.

Many thanks for your experience and input.
Ken

Thats cool.... just trying to save you fixing something that may not be broke :tongue:

Won't hurt to pop another earth between the tank and chassis if you have the time and bits tho. Thats another very common issue
Doesn't have to be heavy gauge wire like a battery earth or you can wait and see how you go

[57flw]

Hi Guys,
Thanks for your help so far.

Here is where I am up to now.
Battery has been disconnected for three days.
New alternator fitted, output is 13.8 Volts.
With engine running sub tank light on the dash is still lit up. When I operate the sub tank switch nothing happens. Sub tank is 3/4 full and main tank is nearly empty.
The light on the switch does not come on. With the plug to the switch removed I find 4 terminals on the bottom in a row and one at either end on the top. Total of 6.
There is only power at the lower left hand terminal.
Can I use the power available here with a jumper wire to see if the switch is faulty? If so, How?
Is there anything else I can try?
Regards
Ken

[Yendor]

Hi Guys,
Thanks for your help so far.

Here is where I am up to now.
Battery has been disconnected for three days.
New alternator fitted, output is 13.8 Volts.
With engine running sub tank light on the dash is still lit up. When I operate the sub tank switch nothing happens. Sub tank is 3/4 full and main tank is nearly empty.
The light on the switch does not come on. With the plug to the switch removed I find 4 terminals on the bottom in a row and one at either end on the top. Total of 6.
There is only power at the lower left hand terminal.
Can I use the power available here with a jumper wire to see if the switch is faulty? If so, How?
Is there anything else I can try?
Regards
Ken

No you can't. I have already posted the wiring diagram for the switch above, it only switches earth to the control module.

You can try bridging pins 1 and 2 together or you can check for continuity at pins 1 and 2 at the switch, when the switch is on.

If you let me know if it's built before February 2000 or after February 2000 I can tell you how to manually bridge the control module to see if the fuel pump works.

Here is how to perform the self diagnoses.

[57flw]

Rodney,
Build date is 08/00.
I have continuity on the switch between pins 1 and two with the switch pushed in. When I release the switch I loose the circuit. Is this push in switch a momentary switch?
Nothing happened when I bridged pins 1 and 2 at the switch plug.
I did view the wiring diagram for the switch you posted and did not see how to test the switch other than what I have just done.
As mentioned earlier the owner has never seen the transfer pump in action.
Ken

[Yendor]

To check if the pump works disconnect the connector at the sub tank control module and bridge power into pin 2, the G/B (Green with a Black trace wire).

I don't know for certain if it is a momentary switch but at a guess I would say it is.

I haven't heard of a sub tank switch failing yet, as long as you have put it back together correctly it should be fine.

[57flw]

Rodney,
Took power from pin 1 W/B with the connector disconnected and the ignition on, jumped to pin 2 G/B and nothing happened. Does this indicate pump is not working and if so I suppose you will tell me it is inside the sub fuel tank.
I appreciate the help you are given me.
I have told the owner I will not charge her for the time to diagnose this thing. The cost would be huge and she is a single Mum and I am such a nice Guy.
I do not want to let the challenge of the transfer pump beat me.
Ken

[Yendor]

As long as pin 1 did have power and the fuse is not blown.

Next you will need to check the power down at the pump.

I think the petrol pumps are in the tank and the diesel ones are mounted in front of the sub tank??????

There is an inspection cover under the carpet in the floor below the RHS rear seat that should allow you to access the pump if it is in the tank.

[57flw]

Test light showed I had power at pin 1.

Your description of how to get to the sub tank inspection plate was spot on.
Here is what I found. See picture.

What do you advise now!

Ken

[Yendor]

So you have power in the Green with a Black trace wire (with the ignition on and pin 2 bridged at the module?) yes?

Check the large black wire beside the G/B wire make sure it has a good earth connection.

If you have power in the G/B wire and an earth in the Black wire then the pump should be running.

You will need to remove the sender unit from the tank and check the pump and connections.

[57flw]

Have power at the G/B with ignition on and pin 2 bridged at the module plug.
Good earth at Black wire beside G/B. Pump is not running.

At no time have I seen a light come on the sub tank switch when I have operated it.
By the way, does this transfer pump operate automatically at any stage. eg. when the main tank gets to half etc.? or do you have to push the switch.

I will remove the pump tomorrow.
Ken

[Yendor]

If you have a good earth to the pump and you supply power to the pump it should run.

The light in the switch won't come on until the module is able to switch on the pump and fuel is pumping.

Every time the vehicle is started the module performs a test on the system, this includes pumping a small amount of fuel.

Otherwise you need to push the switch to get fuel to transfer.

It is possible there are other faults with the system. First off, you need to find out why the pump is not running when you are suppling direct pos and neg to it.

It might also be a good idea to drain the fuel from the sub tank and flush the tank out. If the fuel has been in there for a long time it might have gone off.

[57flw]

Rodney,
Just a quick question.
If I have power at the G/B wire at the tank with the module bridged why is there no power at the G/B wire with the module plugged in?
Ken

Couldn't wait till tomorrow. Pulled the pump out. Put power to it and nothing happens.

[Yendor]

When the module performs the self test and it detects a problem it will turn off the power to the pump.

How is the sock on the bottom of the pick up? is it full of crap?

[57flw]

Re the power to the pump.....that makes sense.
The sock is quite clean and tidy.
I put power to the pump whilst it was still in the tank as well as after I removed it. Definitely is not working.

Will need to wait a few days for a replacement pump then try again.

[Yendor]

If you have to get a genuine pump try sending Nizzbits a PM, on this form. Gary is the cheapest around for genuine parts.

Hopefully the pump is your only problem and once replaced the system will work correctly.

Cheers Rodney

[57flw]

UPDATE

Owner got hold of a genuine second hand pump which I fitted (after testing it of course).
Sub tank light on the dash went out when the engine is started.
I pushed the sub tank button and the small green light came on and the transfer of fuel happened as it should.
When the fuel transfer ended the sub tank gauge showed empty and the sub tank light on the dash came on again.
I half filled the sub tank with new fuel and disconnected the battery for an hour.

Both tanks show half full. Engine running the sub tank light is off.
Question 1. Do you have to manually push the sub tank button to do a fuel transfer or is it done automatically when the main tank gets down a bit.
Question 2. If I manually operate the sub tank switch do I have to operate it again to stop the fuel transfer.

Ken

[the evil twin]

UPDATE

Owner got hold of a genuine second hand pump which I fitted (after testing it of course).
Sub tank light on the dash went out when the engine is started.
I pushed the sub tank button and the small green light came on and the transfer of fuel happened as it should.
When the fuel transfer ended the sub tank gauge showed empty and the sub tank light on the dash came on again.
I half filled the sub tank with new fuel and disconnected the battery for an hour.

Both tanks show half full. Engine running the sub tank light is off.
Question 1. Do you have to manually push the sub tank button to do a fuel transfer or is it done automatically when the main tank gets down a bit.
Question 2. If I manually operate the sub tank switch do I have to operate it again to stop the fuel transfer.

Ken

1. Yes, to transfer as opposed to self test you have to push the button

2. Yes, to stop the transfer you have to press the button again. It will also stop automatically when the sub low level switch activates or the main tank exceeds a set level. To recommence transfer after the main drops a bit you need to push teh button again

[57flw]

Well, in that case I reckon it is now working great.

Want to thank you guys for all the help I have received from this Forum.
I have recently finished a complete restoration on my 1957 Cadillac and not once did I have to disconnect the battery for a period of time to rectify a fault. No ECU or MAF or any other letters in my car. No plastic either.
The owner is very happy with the work I did on her Patrol and said she will only let me work on it from now on. Lucky me!!
I made sure I acknowledged the forum help to her.

Once again. Thank You all.
I am sure I will need further help at some stage and of course I will chip in any assistance I can give other users.
I may be an old retired Army mechanic but I still remember which end of a screw driver to use.

Regards
Ken

[Yendor]

Hi Ken,

Glad to hear you have had a win.

I am a little concerned about this




When the fuel transfer ended the sub tank gauge showed empty and the sub tank light on the dash came on again.



The only time the sub tank warning light in the dash should come on is when the ignition is turned on and it should go out as soon as the engine is started.

If it comes on at any other time it normally indicates a problem.

Hopefully is was only due to the new pump being fitted and now that it has done a pump cycle and you have reset it by disconnecting the battery it should all be good.

It may pay to try transferring all the fuel from the sub tank again and see what happens.

Cheers Rodney

[57flw]

Rodney,
I was a bit concerned about that as well.

I now have a reasonable understanding of how this thing works. Perhaps the sub tank low level switch (wherever that is) is a problem.

I will get the owner to try another fuel transfer.
Once again. Many thanks for your help.

Ken

[57flw]

Owner took the vehicle on a run from Hervey Bay to Brisbane and back and it went like a charm.
She did a fuel transfer during the trip and everything performed well.
That makes another happy Patrol owner and I, with a lot of help from this Forum, learnt plenty.

Thank you all.
Ken

[Yendor]

Thanks for the update Ken. It's good to hear it's going well.

Cheers Rodney