I have an 04, X3 with 133 k. For a while the fuel gauge has been slow to rise to full after adding gas. My wife recently ran the car out of gas. After refueling I observed that fuel gauge will not go pass the 1 O'clock position (slightly above 1/2 ) even though I know it is topped off with 18 gallons. I believe one of the two fuel sensors is the culprit. I have read a lot about ethanol and bad gas being the cause. Techron fuel additive even addresses fuel gauge corrosion on their sales page. So I put some in and will wait for a few days but I am not betting that will cure it.
There are actually two fuel level sensors each costing $105, they don't look to hard to install but does anyone how to determine which sensor is the culprit. Unfortunately they are different parts and not interchangeable. Has anyone had this issue ?
The two sensors are variable resistors as the fuel level rises the resistance goes up to 400 ohms per side. I am assuming that because they are in the same linear series circuit that 800 ohms of resistance is converted into an analog value represented by the gas gauge. My guess is that because the onset of this problem was incremental as opposed to abrupt that it is not a mechanical failure e.g float fell off .
Another assumption, could this be remedied by gently cleaning (pencil eraser) or chemically cleaning the contacts on the contacts on the rheostat ?
Any help would be greatly appreciated ,
The fuel sender signals go both individually to the cluster, which then determines the "combined" value. The easiest way to debug is to enable the cluster test function, and there is a specific test (I believe it was #6) which shows the two individual values. The sender that has the issue has either an erratic or stuck value.
If the gauge does not go empty, you may also have a problem with a siphon hose between the two halfs of the tank and not necessarily with the fuel senders.
It should be farely easy to figure out what the problem is. The somewhat harder part is to open the tank and replace any of the components.
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