Incorrect Fuel Gauge Reading

[Palex12]

Hi!
Earlier, my 2015 C5 ehdi had difficulties with refueling. I could refuel at 80% capacity with the pump nozzle; otherwise, the overfill protection would engage. It has been hot recently, and it seems the problem worsened while refueling. However, I managed to get a full tank, but now the fuel gauge shows 7/8. I drove 100 km, consuming 5 liters. Today, I added fuel, but it didn't go in properly. Still, I assume the tank is full, but the gauge didn't rise and shows 3/4. Could it be that the BSI unit is confused, or is the problem physical in sensor? Or could there be pressure in the tank?
I would be grateful for opinions and advice.

[Paul-R]

I believe that filling with less than 10 litres is not enough to register on the fuel gauge. You don't say how much the second attempt was. Could it have been less than 10 litres?

[GiveMeABreak]

Hi!
Earlier, my 2015 C5 ehdi had difficulties with refueling. I could refuel at 80% capacity with the pump nozzle; otherwise, the overfill protection would engage. It has been hot recently, and it seems the problem worsened while refueling. However, I managed to get a full tank, but now the fuel gauge shows 7/8. I drove 100 km, consuming 5 liters. Today, I added fuel, but it didn't go in properly. Still, I assume the tank is full, but the gauge didn't rise and shows 3/4. Could it be that the BSI unit is confused, or is the problem physical in sensor? Or could there be pressure in the tank?
I would be grateful for opinions and advice.

This can happen after over-filling. Never fill past the third click. It's happened to me and others in the past. What you can do is to run the vehicle to near empty (just under a quarter of a tank), then fill the tank up to the click, then see if the display resets back to full.

Doing this can correct it. If it still isn't working after you've tried this, then the dealer can this sort out by checking the fuel gauge law is correct and recalibrating it if necessary, after checking that the gauge is not stuck or damaged.

[Paul-R]

Can I introduce a reality check on this propagation of the mantra "don't fill up beyond the first (or second, or third) click"? I have always filled my fuel tanks up as much as I can in 55 years of driving. I have never had a problem with this providing I'm careful to trickle the last few millilitres after the first click. This continues to be the case on our 2013 and 2015 cars.

As I posted above I believe the problem may be because too little fuel was put in to register. As an example, a few years ago we had a problem with the fuel pump in our 2001 Citroen Xsara. I put 5 litres of fuel in in case the nearly empty tank was, in fact, causing the problem. It made no difference and I put another 5 litres in to see if it would then start. No change so another 5 litres went in. Still no change so we had to be recovered to a Citroen dealer where a new pump fixed the problem. But, the point is that the fuel gauge didn't move at all with the extra 15l of fuel as it went in 5l at a time.

[GiveMeABreak]

As you know by now, I'll only provide the manufacturer recommendations on these sorts of things as they're obviously there for a reason. The filling levels / clicks are not mantras but facts as stated in the owner manuals.

So while we're on this subject, here are the facts which relate to the OPs vehicle:

Fill the tank, but do not persist after the third cut-off; this could cause your vehicle to malfunction.
Additions of fuel must be of at least 5 litres to be taken into account by the fuel gauge.

[Palex12]

Thank you for the helpful advice. I didn't know that small refueling is contraindicated. I will keep that in mind. If the method with emptying the tank doesn't work, how do I calibrate in DiagBox, or is it better to leave this to professionals?

[GiveMeABreak]

There is a procedure that needs to be undertaken to check that the gauge corresponds to the actual fuel - so involves measuring against the fuel laws for the specific vehicle and engine. I'd try my suggestion above first and you may find that it will come back on its own.

[Palex12]

I filled up 60 liters, and now the reading is correct. Just a small bug.
Thank you all for the tips.

[GiveMeABreak]

Great, glad it helped, thanks for the feedback and update.