AGAIN - inaccurate fuel level problem

[simoncpw]

My car keep having problem with the fuel level meter, still reads low or no fuel even after refueling to full tank...

Back in May, I already had both the fuel level sensor and fuel sender changed. But about a month ago, the problem came back again. I first had the fuel level sensor replaced (it was found broken and started to fall apart), it worked fine but problem came back after only one full tank of fuel. Then the fuel sender was replaced as well.... all seemed to work fine... until tonight, the fuel level was wrong again:

I had about 1/8 tank left (orange light was not lid yet), decided to drop in the fuel station to refuel to full tank. After start up, the fuel level meter remain as before (1/8 tank) instead of showing full tank. Base on the last experience, the fuel level will just keep dropping as I drive, until the orange light comes... then it just stuck there even though the are still a lot of fuel.

1) Has anyone had such problem before?
2) What else could this be besides the sensor and sender?
3) Would putting too much fuel in the tank cause damages to the sensors?
4) Anything to do with using 95 (instead of 98) octane fuel?

ANY advice would be greatly appreciated.

[Weasel]

Wow, that's uncommon, usually people are exactly 1/2 a tank off when they have fuel gauge problems. BMWs have a 2 sided saddle tank and have a fuel level sender on each side. Did you change both sides already? If you did I would want to know the level readings from each side at full tank when reading correctly, and from each side when full and it is still showing empty... reason being to see if the problem is with the sensors themselves or with the instrument cluster interpreting the readings.

I wish I had my training books handy so I could scan some pages on unlocking the service menus in the cluster allowing you to get the readouts of what it is seeing in liters from each side of the tank.

[simoncpw]

Hi Weasel,

Yes, both sides (item 1 and 3 here) were replaced.

Unlocking the service menu in cluster... do you mean this?

[simoncpw]

I gave it a go.... managed to get the hidden OBC service menu to display by pressing the OBC message selector (not trip reset) + switch key position 1. However, I was unable to unlock menu 19 to display menu 3 to 18.

But when I tried Trip Reset + Switch key position 1, I got the following:

[Weasel]

Yeah, that is the menu I was talking about, figures it would be on this very site.

The menu pulled up in the pics is the one to reset your oil service counter though. You would need to turn the key to full on to get to the menu from the link.

So 19 to unlock, and 6 shows left side / right side fuel readings in liters. (but hard to determine what you're looking at) Would be good to see and note down what it says at full when it is reading correctly, then what it is saying when full and reading near empty... then compare.

[simoncpw]

Any idea how to set 19 to unlock? I managed to pull up the menu by using the check botton (#8 from the pic below), but unable to change the setting:

1) press Check selector + key swith from position 0 to 1
2) "Test NR-1" is displayed
3) press Check selector to go down to "Test NR-19"
4) press Trip Reset, displays "Lock: ON"
5) press Trip Reset again, changes to "Lock: 00"
5.1) press Trip Reset again, changes to "Lock: 01"
5.2) repeat 5.1... and it goes all the way to "Lock: 45"

There's no unlock option

[Weasel]

The info and procedures are in my training manuals, but I loaned them to my brother now that he is working with me so he can acquaint himself with the systems... and I don't remember all the details off hand as it isn't something I do often.

[simoncpw]

No worries. I'll try to do more research on this, or might just bring it in to check while I'm on away for this week. Thanks man.

[simoncpw]

Btw Weasel,

Any thought on the below?
3) Would putting too much fuel in the tank cause damages to the sensors? - because I always tried to refill to the FUEL, even the fuel gun has stopped and I manually press a little further.
4) Anything to do with using 95 (instead of 98) octane fuel? - read some post saying that it cause damages to the sensors?

[Weasel]

Filling the tank that much is pretty common everywhere, and won't cause any problems. (I do it too)

We don't have gas with that octane down here... regular is 87 octane, mid grade is 91 and premium is 93. She must run like a scalded beast on 95 or 98 octane!