Our 2017 TDi 4x4 has just started doing it. Our previous one took a while for the needle to move from the top (due to saddlebag tank?), but our current one has done 100 miles without moving. Any ideas?

It may be that the tank was filled right to the brim. I would leave it for another 100 miles. If its still the same it may be a wiring short which I think would read full all the time or the sender unit in tank is stuck. Could also be a stuck guage on cluster. Try tapping cluster but not too hard. You could also try disconnecting battery for a while to reboot ECU etc.

Alasdair

My old Fabia I could go up to 150 miles without seeing a drop in fuel on the gauge. That was brimming it though with a litre plus in the filler neck.

Sons m1 fabia did the same the other day. Fault in petrol pump and it filled it till it overflowed. Took about 150miles for it to start dropping.

Alasdair

It can take a while to show use, especially as the tank is saddle shaped on a 4x4.

Thanks for the replies.

It was actually showing down to 3/4 normally, but in the last 2 days it's full.

If its jumped from 3/4 to full I would suspect a sender fault or wiring short. From memory on modern vehicles the lower the fuel the higher resistance at sender hence a short will be zero resistance so show max. Not sure where the tank is but worth checking wiring to sender in case its damaged/worn. Might be worth getting it scanned in case it pings something up. It also depends if the signal from sender goes through the BCM module or direct to cluster.

Alasdair

If its jumped from 3/4 to full I would suspect a sender fault or wiring short. From memory on modern vehicles the lower the fuel the higher resistance at sender hence a short will be zero resistance so show max. Not sure where the tank is but worth checking wiring to sender in case its damaged/worn. Might be worth getting it scanned in case it pings something up. It also depends if the signal from sender goes through the BCM module or direct to cluster.

Alasdair

Sorry no idea how the above happen. Got message saying your replies have been merged?

Alasdair

Plugged in my Carista dongle and there was nothing in faults in the diagnosis.

BUT, after 120 miles, it's dropped back to 3\4 full now 🙃

Hopefully a glitch. I would monitor it and maybe keep an eye on trip mileage in case the guage/wiring is faulty and showing more fuel than you have. If it happens again I would check wiring from sender backwards.

Alasdair

Is the sender difficult to get to? (My Subaru is under the back seat carpet so easy)

Not sure on the Yeti. Fabia is under rear seat so yeti may be the same. May be under a plastic cover. If the guage is working and then showing full randomly I would suspect a wiring short or broken wire. On some skodas fuel sender feeds direct to cluster and others via BCM. Think it depends on age.

Alasdair

I had a problem with a sender float once, apparently the tank was all but empty.

filling it from empty with the full volume petrol hose had bent the float causing

a poor/non-existent signal.