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BarneyB Profile
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Date Registered: 11-2008
Location: Blakeview, Adelaide SA
TOTAL POSTS: 183
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Re: Series (1 &?) 2 fuel gauge wrong display on full tank defect: fix


Thanks for the info Malcolm, appreciate the photos.

Jalal, I was not seriously asking for a flood of interest, just trying to elicit a response from Malcolm, possibly a poor choice of words on my part.

Tony, no apology needed, I did not see your post before you edited it, working too many hours at the moment to spend enough quality time keeping up with this site.

---
Regards,
Barney X1047 (c)

2008 ST31, CVT, Flint, Towbar, Cargo mat, Headlight protectors, Dashmat, LED kick steps. Bonnet protector
27/Jun/2012, 11:16 pm Link to this post Send Email PM   Send Private Message
 
cooch t31 Profile
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Date Registered: 06-2008
Location: Blue Mountains, NSW
TOTAL POSTS: 5966
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Re:


Thanks Malcolm,
The DIY section would be a better place for this to be in.


---
Tony X-891c

HERE is my D22 Navara
HERE is my old 2008 T31, ST Series1

28/Jun/2012, 6:02 am Link to this post Send Private Message
 
jalalski Profile
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Date Registered: 02-2004
Location: SUTHERLAND, SYDNEY
TOTAL POSTS: 29094
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Re:


Not yet Tony, it needs further confirmation that this solution works and will remain functioning correctly according to what Malcolm mentioned.

Last edited by jalalski, 28/Jun/2012, 6:16 am


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28/Jun/2012, 6:15 am Link to this post Send Private Message MSN Blog
 
Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 5676
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Re: Series (1 &?) 2 fuel gauge wrong display on full tank defect: fix


What it looks like is that the wiper arm has a carbon brush which shorts across the 2 "ladder" track pickups to then give an incemental resistance to the meter. The impurities are just carbon deposits left by the brushes on the ladder tracks and as carbon is conducting, essentially short them out, decreasing the resistance seen by the meter, hence the low readout when full.

If this is the case, which could be confirmed by sighting a new unit to check if the ladder tracks are all clean, then I would suggest cleaning all of the ladder tracks and not just the portion at the end where shown.

---
Kev X450(c) T30 Guru
03 Titanium Ti T30 Series 1 **MODIFIED**
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28/Jun/2012, 4:47 pm Link to this post Send Email PM   Send Private Message Blog
 
mrhox Profile
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Date Registered: 04-2012
TOTAL POSTS: 27
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Re: Series (1 &?) 2 fuel gauge wrong display on full tank defect: fix


quote:

Revhead Kev wrote:
What it looks like is that the wiper arm has a carbon brush which shorts across the 2 "ladder" track pickups to then give an incemental resistance to the meter.



I don't know if it's carbon, but the concept is correct:
Image

quote:

Revhead Kev wrote:
The impurities are just carbon deposits left by the brushes on the ladder tracks...


'Just'... probably right, though I wouldn't discount impurities in the fuel = probably irrelevant.
At the point of contact between the 'brush' and wiper track, there is a very low level electrical interaction taking place. Perhaps, over thousands of back and forth movements, there could be some kind of electro-chemical reaction taking place, leaving a deposit. I'm not a metallurgist, though, so just speculating.

quote:

Revhead Kev wrote:
...and as carbon is conducting, essentially short them out, decreasing the resistance seen by the meter, hence the low readout when full.


But 'shorting' them out would result in a LOWER overall resistance.
Now, since the resistance across the sender reduces as the fuel level gets higher, any additional 'shorting' would create an artificially HIGHER fuel level.
Exactly the opposite is happening (ie: the resistance across the sender is TOO high on FULL fuel level).

((The wiper arm resistance ranges from 80 ohms (EMPTY position) to 2.5 ohms [FULL position on main sender] and from 47 to 2.5ohms [sub sender].))

In fact, if you momentarily short the two sender wires, you get all 13 segments on the fuel gauge.
Here's how: expose the cabling coming out of the driver's side floor plate:
Image
Now, short the thinner pair of wires (the thicker pair is the fuel pump power) and turn on the ignition (no need to start the engine, of course) and observe the fuel gauge.
Note: Use a cable with alligator clips and squeeze firmly to pierce the insulation.

On a full fuel tank, you can also check the combined main and sub fuel sender resistors.
They are wired in series so if one sender has a complete failure, your fuel gauge will display ZERO.

According to specifications, the minimum total resistance is 2.5 + 2.5 ohms (5.0 ohms).
I re-worked the senders this afternoon, using a soft abrasive strip on the wiper tracks and succeeded in getting 13 segments.
10km later and I lost one (what the !@#$!@????) AGAIN!!!

So, using the above approach, I measured the external sender wiring:
Image
That extra 0.9ohms, I believe, is enough to lose a segment.
I'm going to do a parallel resistance experiment to (dis)prove this idea.
Note: Again, use alligator clips. In this case, between the multimeter probes and these thinner wires. You must squeeze the clips so they pierce the insulation. I recommended offset piercing to eliminate any chance of any future unintended shorting.

quote:

Revhead Kev wrote:
If this is the case, which could be confirmed by sighting a new unit to check if the ladder tracks are all clean, then I would suggest cleaning all of the ladder tracks and not just the portion at the end where shown.



Didn't have a new unit, but after cleaning both wiper tracks, it looks a little like this:
Image

Okay, this reply is a little 'all over the place' since I am in the middle of a few other things, but felt compelled to respond.
I would appreciate other people trying the 'wiper clean' concept and provide feedback.

I would LOVE a close-up photo of the Series 3, 4 or 5 sender unit wipers to see what Nissan did to 'fix' the problem.

...

Last edited by mrhox, 28/Jun/2012, 10:03 pm
28/Jun/2012, 9:55 pm Link to this post Send Email PM   Send Private Message Blog
 
xxb4xx Profile
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Date Registered: 07-2012
TOTAL POSTS: 6
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Re:


The sender units aren't hard to remove are they? i'm guessing they are a part of the fuel pump assembly located in the boot of the car?.

From what I have seen there is a sender on each side of the tank, one should be for the top half and the other for the bottom half from what I am aware of?.

Either way, thanks for the pics, i'll be doing this once my tank of fuel is almost depleted!
25/Jul/2012, 12:13 pm Link to this post Send Email PM   Send Private Message Blog
 
mrhox Profile
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Date Registered: 04-2012
TOTAL POSTS: 27
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Re: Re:


I thought I better update this thread.
Seems I've 'irritated' some people by my contributions thus far, either by what I've written or omitted. My life does NOT revolve around my (wife's) Xtrail, but her frustrations often become 'mine', so I do what I can to make things better.

For a bunch of photos I've used to record some of the 'work' on this matter, please refer to
s1240.photobucket.com/albums/gg496/mrhox1
They are meant to form part of a detailed 'how to' guide. Some are self-explanatory, other's need explanation (but can probably be worked out).
After my first 13/13 segment success was not repeated consistently, I've chosen other priorities.

xxb4xx, to your questions:
Hard to remove? In my opinion, yes, if you have never done this kind of thing before (raises hand in affirmation.)

There are two sender units, accessible from under the rear seats, under an access panel.
Yes, one is a combination fuel pump/sender unit. The other is just a sender unit.
I recommend accessing the passenger-side sender first (the non-pump side). It's much easier to remove and re-install..and gives you an idea of what needs to be done and what to expect on the 'trickier' side.

No, the senders are not for the 'top' and 'bottom' of the tank, but to cater for the shape of the tank.
(Someone correct me: It's theoretically possible to completely empty the tank, then only say, one-third fill it, and not have any fuel enter the passenger side of the tank. The limited 'open' design of the tank will, of course, allow fuel to slosh from one side to the other.)

The fuel sender on the passenger side has both electrical wiring (resistance measurement sender) and a fuel conduit connected into the driver's side sender/pump unit.
The pump unit simultaneously draws from both sides of the tank. The intake point is close to the bottom of the tank, obviously close to the 'empty' swing position of the fuel float on the assembly.
These variable resistors are in series. If one sender's resistor module fails completely, you will get zero fuel reading.

Work on an empty tank? Almost: fill up, do 300-400km. Then go for it.

Best wishes.
Please post your results...


Last edited by mrhox, 26/Jul/2012, 9:21 pm
26/Jul/2012, 9:19 pm Link to this post Send Email PM   Send Private Message Blog
 
xxb4xx Profile
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Date Registered: 07-2012
TOTAL POSTS: 6
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Re:


Mate you are Gem,

I did the same pretty much steps for my Subaru liberty when the pump died, identical setup to this as well.

I can see 2 housing's from behind the back seats that look similar to what the pump / sender should look like in the boot.
6/Aug/2012, 8:34 am Link to this post Send Email PM   Send Private Message Blog
 
linezero Profile
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Date Registered: 09-2009
Location: Kellyville, NSW
TOTAL POSTS: 7
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Re: Series (1 &?) 2 fuel gauge wrong display on full tank defect: fix


Interesting - my gauge never reaches the top segment any more, I'll have to see how it goes. Re: 540km on a tank - just about, when I fill up in the ACT with ULP (not E10) and go easy with cruise and do a bit of truck slip-streaming all the way back to Sydney, I only use about 25 litres for 290km...so it is feasible!!

---
Alan X-1414

T31 Adventure Edition Platinum
Plus Nissan Fogs, Bonnet protector, Rear Park Assist
4/Sep/2012, 4:34 pm Link to this post Send Email PM   Send Private Message
 
Translucidus Profile
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Date Registered: 05-2010
Location: Adelaide
TOTAL POSTS: 599
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Re: Series (1 &?) 2 fuel gauge wrong display on full tank defect: fix


At the 70,000km service I mentioned to the dealer the gauge not accurate.

Fuel senders and pump replaced due to "Out of spec".

Love my extended warranty emoticon

Gauge now stays on top bar for about 100kms!!! instead of never lighting top bar before.



---
2007 X-Trail T31 ST-L

Xy going vertical at Bendleby Station . . .

4/Dec/2012, 12:52 pm Link to this post Send Email PM   Send Private Message
 


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