Mystery behaviour at petrol station

[Vicario]

I had a strange experience when filling up today. Micra 2020 (auto) petrol engine. I inserted the nozzle and began to fill. It felt as if there was a bit more pressure needed on the trigger. Put £15 worth in, so nowhere near enough to fill the tank. Paid and came to move off. Car went into limp mode with the check light on, rock hard brake pedal - you know the drill. Anyway, I switched off and on again, then selected Low gear and managed to move off. Petrol gauge was showing full, so totally incorrect. I parked round the corner, switched off and waited for 5 minutes. Switched on again and all OK, apart from the gauge which took about 15 minutes to settle at about 2/3 full. Has anyone got an idea what might be wrong? It was definitely petrol that I put in, by the way.

 

[Wayners]

I have a ford and if I turn engine off and start again quickly the fuel gauge is incorrect. Shows way less than is in tank. I need to turn ignition on and wait 2 seconds before stating so guage settles

 

[Burnerman]

Although I’ve no idea what’s going on here I certainly wouldn’t worry about it unless it happens again.
However, there will be a fault code stored which can be read if you want.....it’s probably to do with the emissions system, namely the fuel vapour in the tank which is inhaled and burnt by the engine.
John

 

[Koolpc]

I have a ford and if I turn engine off and start again quickly the fuel gauge is incorrect. Shows way less than is in tank. I need to turn ignition on and wait 2 seconds before stating so guage settles

Sometimes that happens with my car too.

 

[Harry Bloomfield]

Petrol gauge was showing full, so totally incorrect. I parked round the corner, switched off and waited for 5 minutes. Switched on again and all OK, apart from the gauge which took about 15 minutes to settle at about 2/3 full. Has anyone got an idea what might be wrong? It was definitely petrol that I put in, by the way.

My fuel gauge isn't what would at one time be called a fuel gauge at all. It has a saddle shaped tank, with two level sensors, which feed data to an ECU, the ECU then feeds an interpretation of the tank contents, to the gauge. The interpretation, includes a factor for the rate of fuel consumption. It also recalibrates its idea of what is a full tank, when you completely fill the tank. Start the car in the garage, and the gauge will read a bit low, but then as the car gets out on the road, and mpg increases, the gauge rises to a more realistic level.

If yours works something like this, maybe the ECU just got confused.