[x.zhang]

hey everyone, my 2011 535i, 60k miles, recently developed a weird issue. the pointer in the fuel guage some times doesn't reflect the refill. for example if it's half a quater left (say 50 miles range left), then i went for a full refil and keep driving, the pointer would stay at the half quarter scale and slowly move toward the empty side along with the range that would drop from 50 to 49, 48.... just as i never filled the tank up. some times after i completely shut off the car and restart, it went back to normal. some times it would only become normal over night.
i wonder if anyone has experience this kind of issue? Any input is appreciated! Have a nice weekend.

[Surly73]

Originally Posted by x.zhang

hey everyone, my 2011 535i, 60k miles, recently developed a weird issue. the pointer in the fuel guage some times doesn't reflect the refill. for example if it's half a quater left (say 50 miles range left), then i went for a full refil and keep driving, the pointer would stay at the half quarter scale and slowly move toward the empty side along with the range that would drop from 50 to 49, 48.... just as i never filled the tank up. some times after i completely shut off the car and restart, it went back to normal. some times it would only become normal over night.
i wonder if anyone has experience this kind of issue? Any input is appreciated! Have a nice weekend.

Are you shutting off the ignition while you are adding fuel?

[x.zhang]

Originally Posted by Surly73

Are you shutting off the ignition while you are adding fuel?

the engine was shut off for sure. But normally the infotainment system stays on unless the car is locked.
i remember that i used to see, could be on other cars, the guage pointer moves to slowly toward right (full) while refilling, which means a complete power off during refill isn't really neccesary?

[wcr3d]

If you searched here and haven't found anything try www.bimmerfest.com , I have read some threads there that are similar or the needle never moves kind of thing.

[Surly73]

Originally Posted by x.zhang

the engine was shut off for sure. But normally the infotainment system stays on unless the car is locked.
i remember that i used to see, could be on other cars, the guage pointer moves to slowly toward right (full) while refilling, which means a complete power off during refill isn't really neccesary?

Alright. During my time with older BMWs (E39, E46) I recall people describing exactly what you describe if they leave the ignition on while refueling so it would be the simplest explanation.

Your ignition should be in a state that your fuel gauge does NOT read while you are refueling. If that's not what you're doing, start doing it that way and see if your problem goes away. All of the range tracking/forecasting and other system do not expect fuel to be added while the system is on and don't reset or act properly.

[x.zhang]

Originally Posted by Surly73

Alright. During my time with older BMWs (E39, E46) I recall people describing exactly what you describe if they leave the ignition on while refueling so it would be the simplest explanation.

Your ignition should be in a state that your fuel gauge does NOT read while you are refueling. If that's not what you're doing, start doing it that way and see if your problem goes away. All of the range tracking/forecasting and other system do not expect fuel to be added while the system is on and don't reset or act properly.

hey, thanks for your replies.
when i went through the repair manual how the fuel level sensors function i found out that, when either one or both of the sensors (driver and passenger side of the tank) is detected defective, the control unit kicks in and the fuel level in the guage is instead CALCULATED by the consumption from the last point the sensor worked properly. This totally explains the weird bahavior of my guage pointer. I assume the bad sensor in my tank is not completely off so whenever the control unit picks up a signal from it the guage would return to the actual position, otherwise the pointer stays at a calculated.
I could only hope the one with the pump (passenger side) is bad because that's the one serviceable while the driver side float assembly is embedded inside a closed tank, only a pair of wires plugged into the pump assembly.

[550iFreak]

Look up if you qualify for replacement from the recall. There is a recall on the fuel sending unit but it a long time ago. See if yours has been done or not.

Mines was under recall on my 2011 550i, but I have a complete fuel system overhaul before purchase in 2016 so I'm good to go for a long time hehe.

[Surly73]

Originally Posted by x.zhang

hey, thanks for your replies.
when i went through the repair manual how the fuel level sensors function i found out that, when either one or both of the sensors (driver and passenger side of the tank) is detected defective, the control unit kicks in and the fuel level in the guage is instead CALCULATED by the consumption from the last point the sensor worked properly.

Nice find!

[x.zhang]

actually a couple of week back the dealer here just got my fuel pump replaced at no cost, somehow the floaters were not included

[550iFreak]

If your fuel pump was just replaced at the dealer, then it is highly suggested to go back to resolve the issue. Unless the issue was there prior, it is a good idea to head back.

The sensors or floaters should be part of the recall. It said it in a way that exactly explains the issues you are having right now.

On mines, when the power is on, the gauge moves as fuel is filling the tank.

And obviously when it is off and then turned on after fueling, it shows a new reading( usually in full).