The last few times I have put petrol in my car, the needle showing on the guage of the dash hasn’t moved. It does not go up as the tank fills, nor when I’ve finished.
This is odd, it always behaved until recently, and it is also a nuisance because I don’t know how much petrol I’ve got in there.
What could be causing this, is it sludge in the tank, and is it an expensive problem to sort out does anyone know please?
It’s a Fiat.
Can’t help there Mups, sensor or the gauge? One of the petrol heads on here will advise.
OK, thanks anyway, Vlad. x
I will wait and see if anyone has any bright ideas.
Hi Mups. Maybe tap the gauge gently just in case the needle has stuck. Or possibly get a strong young man to rock the car side to side. Get out first of course. 
I always make a habit of resetting the mileage trip meter to zero on filling the tank, that way I know roughly the miles I have done whatever happens. At 58mpg and knowing both the tank capacity and how much fuel was purchased, it’s easy enough to work out how much fuel has been used and fill up when required. 
I don’t know the modern cars any more, computers on wheels nowadays, too much like my laptop. At a guess it’s possibly a faulty sensor or it could be a loose connection.
Probably a problem with the sender in the fuel tank Mups. Sometimes these are easy to get at through the boot floor, and sometimes it means removing the fuel tank, but I’ve no idea on cost you would have to ask at the garage.
However, if you aren’t bothered about it too much you could just fill the tank each time you put petrol in and keep a note of the mileage using the tripometer to give you an idea how much you have used, a couple of times doing this after around two hundred miles should give you a good idea of your average mpg, if you don’t know already.
I agree, the sender sounds like the problem or the float is stuck inside the tank. Not normally a difficult job to fit a new one.
In one of my old cars, my petrol gauge would actual go UP whilst I was driving. That turned out to be a loose wire from the sender, touching the bodywork.
Most cars manufactured in the past 20 or so years have a delayed fuel gauge to stop any needle bounce from the fuel slopping around the tank while driving. If yours does not move after say around 3 to 5 mins after filling, then I would suggest your sender unit in the tank needs removing and checking or replacing after the wiring/grounding had been checked.
best let a garage replace the sender, easy enough to do the only problem is making sure the gasket is sealing the sender to the tank properly or you will get petrol fumes in the car. Unit should cost around £25/30 plus fitting so not an over expensive item to replace.
Done that job a few times in the past it is the petol fumes that get you
What fiat model is it mups…?
It’s a little Fiat Panda Easy, Primus.
Thank you for all your suggestions folks, much appreciated.
Just one more thing though, if it is the Sender - what the 'eck is a Sender?
Never heard of it. 
P.S. Nipped out to the local shop just before it got dark tonight and I see the guage has moved to where it should be.
Wonder why it’s taking about 12 hours to do that though?
That’s my technique too I know I can get about 700km out of a tank. You soon get into the habit, I use “A” trip meter for individual trip distance, “B” for fuel consumption.
Having said that the fuel gauge is actually pretty accurate
That sounds like the float is sticking, it’s located in the fuel tank, if it’s run a bit low and not used, it may have stuck down, and not risen until the pressure of the fuel in the tank has pushed it up, ( think cistern ball clock) , if it keeps happening, you need to get it looked at
I also use both the petrol gauge and mileage trip so that when it’s on ‘half’ I fill the tank, that way
I always have at a minimum half a tank of fuel, if for some reason I cannot get to the petrol station. Old habits die hard! 
Cars these days are like laptops on wheels, the onboard computer can be used to check fuel consumption, which I do occasionally. The VW Golf 1.6 diesel I drive returns 58-61mpg (93-98km to 4.5 litres), hopefully conversion is correct, which I reckon is brilliant. 
Fiat Mupster. :-p
My car is not that sophisticated the next model up has all that gear but I decided I could find out the temperature outside by opening the window so I just keep a record of fuel on a spreadsheet.
I don’t get anything like the economy that you do but it is a 3 litre turbo diesel driving a 2 tonne vehicle so about 10L/100km is not bad especially as those figures are towing a camper too.
BTW I used to think the “litres per 100km” was a daft measure but I must admit it is actually very useful and like it now.
Thats what I do too, Baz. I fill up when it gets down to the half way mark.
That makes sense Primus, thank you.
I think its due for a service next month, so I’ll mention it to them if it’s still happening then.
I assume it’s safe to leave for a few weeks?
Oh you shush.
