Fuel gauge not working

[tiff_lee]

Ok as per title my fuel gauge isn't working.

To eliminate the clocks and the wiring from the tank to them as the fault I removed the three pin plug from the top and shorted one of the orange wires to earth and the gauge then started to go up until full.
Shorting the second orange wire appeared to do nothing, not sure what it is for, haynes says fuel trip computer or something I can't remember but it's item no.340 in the wiring diagram anyhow.

So what are my options now, replace the sender? Or is there some simpler common fault with these?

[Woznaldo]

Have a look at this:

http://www.rtoc.org/files/Technical%20Files/Wiring%20diagrams/WD046%20FUEL%20TANK%20SENDER.JPG

and the aux pump timer, as the sender circuit runs through it:

http://i196.photobucket.com/albums/aa40/woznaldo/R5%20GTT%20Wiring%20Diagrams/Auxillaryfuelpump.jpg

[tiff_lee]

Ok so where abouts on that diagram is the three pin plug on top of the tank?

[Kris M]

the one that reads "fuel tank sender unit"

[tiff_lee]

lol ok I probably seem a dumbass now! only asked as three wires come from the top of my sender supposed to just the two in the diagram.

Surely my aux pump timer is fine though as my gauge works when shorting the signal pin to earth?

[Harrison01]

Have you been able to sort this out yet?

i had same problem and found the cause of mine today!

when i removed the sender unit and took it apart i found that all the little contacts that the slider make contact with were disintergrating and coming off and therefore not giving me a reading.

[tiff_lee]

Haven't had a chance to look further into it yet, however given a change in my circumstances and picking up a new turbo motor tomorrow I am just going to strip the 5 for a track car which will mean losing the standard tanks.

[Jono]

How does the orange low fuel light fit into this.

its probably on the diagram , i just dont know the symbol.

[Woznaldo]

I'm firing this thread up again as I now have a problem with my fuel gauge and want to better understand the system and how it works. I've added another wire diagram but I want to see if my reasoning is logical.
http://i196.photobucket.com/albums/aa40/woznaldo/R5%20GTT%20Wiring%20Diagrams/WD046FUELTANKSENDER.jpg

OK '247' is the instrument panel, the black & white check circle is the low fuel warning light and the gauge looking thing is, well.... ....the fuel gauge:sad2:. Both sides of the circuit share the same 12+v supply (which is the generic instrument panel supply) and therefore must be a switched earth system.

When the fuel sender unit float reaches a certain low level it sends the 12v coming from the 'low fuel warning lamp' to earth, thus completing the circuit and illuminating the light?

On the fuel level side there must be a variable resister in the 'fuel sender unit' (dependent on fuel level) that limits the amount of earth that the gauge sees, thereby setting the gauge level?

Does this mean that if I pull the plug off, with the ignition on, that I should be getting 12v+ at pins 2 & 3?

At the moment I have 12v+ at pin 2 but only 5v+ at pin 3?

The only variable in this system is, why is pin 9 on '247' (instrument panel) coming from the fuel gauge, going to earth?

Just like tiff_lee, if I short pin 3 to earth, the fuel gauge goes to full?

Any ideas? Is my analysis sound?

Small safety point: If you do not know if the sender unit is serviceable, make sure the fuel tank is less than 2/3 full or when you remove the pipes fuel will piss everywhere!..... ......or so I've heard:ashamed:.

[Woznaldo]

Just a small note on the system in general, it would seem that only the low fuel warning light goes through the aux fuel pump timer and that the gauge itself is independent.

[Nick k]

I wrote this in may last year,

*Right, spare sender in a million bits now!!:)

Going from the black wire 1. right side of connector
Orange wire 2. middle
Orange wire 3. next to the renault symbol on the sender plastic.

When the tank is empty you should get about 3 ohms on between 1 and 2 and 283 ohms between 1 and 3 / 2 and 3.

pins 1 and 3 are the fuel gauge. it reads 283 ohms empty and about 10 ohms when full, which makes sense.*

From what i can remember, when the tank is empty the sender is wired so to give a 283 ohm resistance to keep the gauge reading empty on pins 1 and 3, and 3 ohms across pins 1 and 2 to fire the aux fuel pump ( this is when totally empty) when the sender float rises off the bottom it goes back on the normal resistive tracks in the sender and removes the 3 ohms off 1 and 2 and gives the varibles resistance as the float moves up and down on 1 and 3.

The sender does come apart and consists of metal tracks on a pcb type board and conductive wiper arms that travel up and down with the float. Also it have 3 connections at the top which do corrode. My bet is that is the 3 connections causing the issue.

9/10 fuel gauge issues are caused by the sender unit and its crap 3 pin plug.

Did look at the circuit above but my brain has just melted :(

[Woznaldo]

Thanks for the reply Nick, gives me something to measure.

[Woznaldo]

Just measure the resistance between pins 1 & 3 on the sender (with the plug off) and got 300 ohms with the tank toppers with juice? Sender is obviously not playing the game :cry:. It will have to stay like that until I use some of the fuel.

How did you pull the sender apart? I had a quick look while it was off before and the screen filter just pulls off but, where do you go from there? I'm reluctant to experiment with a part i'll have to wait a week for it to come from UK to replace.

[JRP]

doh wrong thread

[Woznaldo]

errr talk about good darts! TENSE I SAY TENSE

:laugh:

[JRP]

doh sorry

[Nick k]

Sounds like the float is stuck on empty. Is that what the gauge is reading? When you pull the sender out there is a metal tube that pulls off and then you can get at the track/float assembley. Might just need roughing up abit to free the float! :agree:

[Woznaldo]

When I had the sender out yesterday, I couldn't seem to get the metal tube off? I held back the 2 plastic hooks at the base but, it looked like the metal tube still had it's own deformed hook pressed into the side?

I'm not going to attempt to pull it out again until I've used some fuel.

[Woznaldo]

I went for a very short drive (on a private road) and the fuel gauge started working intermittently! Probably just a sticking sender unit.