Fuel gauge/sender issue

[Kenclarke]

Need some help with fuel gauge/ sender problem please.
When I bought my e53 a month ago the fuel gauge was showing empty with warning light on. Went out and bought another sender unit for passenger side(non pumped) to find out there was no issue with this sender. So went and got the drivers side sender(pumped) and fitted it. Fuel gauge went up to half, put some diesel in and went to about 3/4 tank. Drove around for a few days and tank showed just below half where it stayed for next few days not dropping anymore. Thinking some was wrong I had sensors out again but no change. Even when both sensors have the plugs disconnected the gauge goes up to just below half when I switch ignition on. Any ideas anyone?

[X5Sport]

The Sender unit is a resistance device so as the resistance changes with the height of the float, the gauge moves. It sounds like you may have an issue in the wiring between the sender units and the front of the vehicle with a 'high resistance' joint issue meaning the gauge isn't getting the right information. The system uses the measured resistance from both senders to determine actual fuel level.

It could be a corroded plug/socket or damaged wires somewhere between the two ends. That could be under the back seat or along the wiring harness to the front, or the connection on the back of the cluster. Yoiu're going to need to follow the wires. Any sign of damp anywhere below the carpets is a good sign that corrosion has upset the loom somewhere.

....and to the Forum

[Kenclarke]

Yes I suspected as much, if it’s reading something there must be a crushed wire shorting somewhere, as reading half tank when no sender unit plugged in. Does one side read empty to half and the other side half to full or doth they both work in unison?

[X5Sport]

From what I have read it’s a combination of the two senders. The tank empties from both sides at once.

[mikeaj]

Contact cleaner on every connection?