Aygo Fuel Gauge Always Full

[johnydeath]

Does anyone have any experience of this phenomena please?

I've read the threads about how the gauge is inaccurate and that it should go 85-120 miles or so before the top bar disappears. I have put £30 of fuel in and it was full gauge before and after.

I understand that the fuel level sender should swing between around 10-100 ohms resistance to represent full and empty conditions so what I have done is put a 100 ohm and a 50 ohm resistor across what I think are the correct wires on the plug going into the sender unit under the back seat. There are four wires, two slightly thicker (white and black) and two thinner (purple and grey) that I'm guessing are the level signals. In both cases the gauge remains full. The sender itself is showing 15 ohms on those pins.

Assuming I have this correct, then the first part of the fault would seem to be in the wiring or somewhere in the dash electronics, would anyone have any pointers how to progress further please?

[dustyjoe]

Could it be the sensor in the tank?

[Raistlin]

I would give Mr T a call

[Wiz201]

mine is currently 109 miles (reset the mile counter every time I fill up) and from full its gone down to the second marker on the gauge so I think there's something definitely wrong with yours.

[johnydeath]

Thanks for the reply so far, there is definitely something wrong, I don't believe it is the sensor in the tank as I used resistors to simulate full/half/empty levels however that is assuming I have connected them correctly.

[johnydeath]

Update to this - although I'd got the correct wires, the resistors did not have the desired effect and did not change the display hence believing it was wiring or dash.

I've done 200 mile and the sender resistance hadn't changed either so out with the pump and I've found I've been victim of the brittle plastic pin support problem where the pump/sender has broken away. It was sitting in the bottom of the tank so was pumping ok but the float was always compressed meaning full. I found a good picture and some info on the C1 forum - I reckon I can use tie wraps to tightly hold the pins in place, I didn't have long wraps so created some using multiple wraps but then the pump wouldn't go back into the tank as the wobbly bits stuck out. Have ordered some 450mm ones which should do the trick, I'll post a fixed pic once done in case it is useful.

[Planemo]

Thanks for this. Do you recall ever having subjected the car to hard knocks of any kind? Mine rides hard with the coilovers and due to the low ride it has had the odd ground out or two. I will keep my eye on mine but thanks for the heads up as this could have been a lot of time for me to diagnose should I get similar symptoms.

[johnydeath]

Not in my ownership as I've only just bought the car, but who knows what perilous life it led before.

[johnydeath]

Ok so my tie wraps didn't come in time for the weekend and I needed to get it back on the road. I bought a pack of shorter ones from Wilco and connected two together making sure that the joins were not on the outside of the circle.

It's a bit of a lash up but the lip on the bottom ensures the tie wraps don't fall off. I did test the level sender and it appeared ok, connected it up with the fuel pump out of the tank (and empty) and the fuel gauge on the dash moved as I moved the level float so all good. Popped it back in the tank, turned the key a few times to pressure up and it started fine, with a full gauge one bar down. Happy days. Now need to run it to one bar and see if I run empty before then just to give an idea of levels. In reality I'll be filling up half way just to be sure.

Did try the resistors one more time and there was movement on the gauge - a bit erratic but did give an indication the signal was getting there.

Cost to repair - my time and £1

[eygo]

WELL DONE

but

my only concerns with your fix is how will the cable ties be in a petroleum / vapour filled enviroment

could they melt / dissolve due to where they are being used i'm sure they wouldn't of been tested

for use with petrol,maybe you could of used the metal cv boot clips instead

[johnydeath]

WELL DONE

but

my only concerns with your fix is how will the cable ties be in a petroleum / vapour filled enviroment

could they melt / dissolve due to where they are being used i'm sure they wouldn't of been tested

for use with petrol,maybe you could of used the metal cv boot clips instead

Yes good point, it did occur to me and I did consider the stainless clips of a similar build but I wasn't sure how to tighten them. I also considered a huge jubilee clip.

There were some similar questions on the interweb I did look at but no solid answer - the wires that are used for the pump and sender appear to be non-silicon and they have not been affected but I think I will swap to stainless when I get chance even if it is just to have a more reliable ratchet mechanism. One site said black cable ties which are nylon/polyamide are UV and fuel resistant but you just never know do you.

At least the exercise proved what I set out to do.

I've just nipped out and popped one in a jam jar of fuel and I'll monitor it daily :)

[johnydeath]

4 months down the line I just thought I'd update this thread.

Fuel pump and gauge doing well, went down to flashing and did around 10 miles before I chickened out and filled up so quite happy with that (yes I did have a can in the boot :) )

Tapeworm in the jar seems content still so hopefully the repair is going to be good for a long time.

 

 

[Raeman]

Excellent result, glad you got it sorted.

Thanks for the info.

[Phil Penhaligan]

Hi Johnny I did a similar repair as yours but used epoxy resin too. It lasted about a year before failing again. On eBay I found a good pattern part that I just fitted and it works! Note I swapped the original fuel gauge resistor from old onto new as the new one didn’t look as robust. The eBay one cost £60.50 including postage from seller “tshopabs”. All working like new again for £60!!!

[Gary Sheehan]

I too put £30 in to fill to top and the gauge has just dropped at 112miles

[Vandals01]

It is well known that the fuel gauge on Aygo were inaccurate.  On my 2012 Gen 1 model:

6/6 Can last 120-160 miles (depends on how wild I went on the last fill up)

5th bar usually around 100 miles

4th bar 80 ish

3rd bar 80 ish

2nd bar or below, I haven't tested its limit.  If I had a Jerry Can I would.  Furthermore, fuel in the tank actually cools the fuel pump which extends the pump's life.  So it is not a good practise to leave the tank with too little petrol.