Inconsistent fuel gauge

[Patrick Bateman]

Any common or likely issues that could cause this?

This becomes more inconsistent in the last quarter of a tank where it can vary quite a bit. Fuel light can come on way earlier than it should given the needle position.

First sign of a problem was a while ago now when I'd park the car after driving home from work with say 60-80 miles range remaining, needle nowhere near empty and the next morning the fuel light would be on. Needle can then appear low and rise back up again but is ultimately inconsistent.

It never used to do this, nothing near it, and I park on a flat surface.

It shouldn't put the fuel light on and have the range drop dramatically the following morning when I've parked it up with 80 miles range left the night before.

I used to see a comfortable 300 miles on a tank before the fuel light came on, now it doesn't get much past 240. Something is definitely amiss with how the fuel is being measured.

 

[MC1]

Think you can see the fuel in litres by doing the instrument panel diag mode. That will let you see the actual reading in litres to see what’s going on. If it reads totally different the next day (parked on flat ground) then it is probably the sender unit worn out (the fine potentiometer windings break from the contact rubbing them away over the years). Could equally be a bad wire, connection or instrument panel, but less common.

 

[Patrick Bateman]

That's a good shout, do you have a link to instructions for that?

 

[MC1]

Think on the clio it’s hold down the stalk button & turn on the ignition. The dials do a full sweep & then you scroll through the display till you get to the fuel level reading. There are some other readings, the one with a couple of letters and underscores is the instrument panel fault codes (not obd codes). To revert back to normal instrument panel use pretty sure you either turn off ignition again or press the button on the instrument panel (if it has one - look at so many cars ive forgotten which the clio has & i’m not with car at mo). If stalk button doesn’t work then do same with this instrument panel button for turning on the test mode.

 

[Patrick Bateman]

That was easy enough, taken over 5 years to find that out.

 

[Patrick Bateman]

I'll keep an eye on this but these photos show parking up after getting petrol last night (50) and first thing this morning (47).

 

[MC1]

Looks ok as will settle once parked up, see how it goes [emoji106]

 

[Patrick Bateman]

That first one wasn't immediate after parking up, maybe within 20 mins.

I'll check tonight after the car has been sat for a while and compare again in the morning.

 

[Cue]

I do notice this also, but i do park on a hill - when the drivers side is higher than the passengers side, it'll read lower than it should. The other way around and it reads normal, or slightly higher, so I took it as just a gravity and fuel system being drained when parked.

 

[Patrick Bateman]

Finally got a chance to take photos of exactly what I'm talking about. The fuel gauge never used to come on with the needle showing a reading as high as that, at those miles travelled and the range showing a blank.

 

[Cue]

Sounds like a possible sender unit issue then - you'd need to test the unit before outlaying to replace ideally.

 

[Patrick Bateman]

Cheers for that.

Saturday morning had another obvious clanger. Had parked up on Friday night with over 70 miles showing as the range left and in the morning it was down to no reading on the miles left but still at least an eighth on the gauge.

Drove around 40 miles before filling up and it only took 35 litres.

 

[MarcB]

Its a sender unit inside the tank.

Lift the back seat off and pop the plastic cover and its there.

Was told never to open the sender unit when there is fuel inside the tank as it will do something (I want to say implode) as the air get sin or something and does something to the tank.
If you are in there changing the unit i would also get a new seal for it.

 

[Patrick Bateman]

Do you know the part number for a new sender unit or are there quality aftermarket options?

 

[Cue]

Its a sender unit inside the tank.

Lift the back seat off and pop the plastic cover and its there.

Was told never to open the sender unit when there is fuel inside the tank as it will do something (I want to say implode) as the air get sin or something and does something to the tank.
If you are in there changing the unit i would also get a new seal for it.

Yeah - I remember on wheeler dealers, they changed a sender unit and it was mentioned to never do any work on them without first draining the tank a day before so a possible spark (as it's an electrical circuit) doesn't light you up like guy fawlkes.

 

[MC1]

There’s a special renault tool to allow the pump/float collar to be undone/ tightened correctly. Without this it is possible but a bit tricky using a drift, preferably nylon to remove any chance of sparks. Do when tank level is low as a full tank can change the shape of the tank slightly and make the ring a pig to start on the thread, have seen them cross threaded many a time. Helps if someone holds the pump while you refit the ring. Mark the ring before loosening so you get retightening torque correct.
The electrics are submerged, so disconnect battery and connector before opening.
Slightly off topic but think a 747 has wires in wing fuel tanks, one did blow up IIRC with empty tank (most dangerous time due to vapour) but led to a mod of some sort to prevent it happening again [emoji854]

 

[MarcB]

Do you know the part number for a new sender unit or are there quality aftermarket options?

I don't have it too hand but when mine changed I bought a second hand 182 one to fit, anyway turned out it was not the sender unit. I know "Our" specialist has a tool for doing the fuel tank as I borrowed it.
Like I say no matter what be careful as if you thread it or crack it its game over, I would get a new seal and a new collar or even a second hand collar.

There is also two very small arrows (one on the sender unit and one on the collar) and these should line up and stay lined up.