Fuel gauge issues

[amebb]

Hi
I have a diesel X5 that i am having issues with on the fuel gauge.


I found that if i put £30.00 of diesel in the car the fuel gauge rises but, does not come down again. So, it constantly tells me that i have 240miles worth of diesel in the tank.

Previously, when i put less diesel in the car the fuel gauge was working correctly and telling me how much fuel i had etc.


Now, today i checked the fuel tank. I cleaned the float sensors and then tried again, still i was getting the same false reading of 240miles worth of diesel in my tank.

The weird thing was when i unplugged the connectors on the pumps i was still getting a reading of 240miles worth of fuel in the tank.... Obviously, when i unplugged the power connector the car stalled.


So, can anyone tell me what i need to do to fix this issue please?




Thank you

[80stech]

Hopefully someone with more X5 diesel experience will chime in but in the meantime I would say the problem is with the sending units. Not filling the car never puts the wiper into the higher position and there is probably a film built up on the sensor track, sure sounds like that anyway

[andrewwynn]

Did you measure the Ω on the sensors when you cleaned them?

When mine acted similarly I had to disassemble and bend the sweeper in such a way to increase the pressure but also when done you need to reset the computer with option 21 in the hidden menu or the "averages" will throw it off. With any luck you are just seeing the math error.

Start with option 21 that might be your only issue. Confirm with option 6 to make sure the liter readings left and right are reading correctly.

When my right sensor stopped reading I didn't realize for a while because I only filled partial tanks for a while. Then when I did fill completely it only showed 2/3 to 3/4 full.

After I fixed the sender it still showed only 2/3 full until I reset with 21.

[amebb]

Originally Posted by 80stech

Hopefully someone with more X5 diesel experience will chime in but in the meantime I would say the problem is with the sending units. Not filling the car never puts the wiper into the higher position and there is probably a film built up on the sensor track, sure sounds like that anyway

The sensor tracks have been cleaned with contact cleaner.

There is resistance on the track and that changes when the float is moved up and down.

So, it may be something else?

[oldskewel]

I'd bet on there being a problem with one of the senders, but if you want to rule out a problem with the instrument panel, you could try putting your own resistor in the circuit to simulate a different sender reading.

I don't know anything beyond my 2001 3.0i, but here are some notes from when I was debugging a problem once (I don't think I had any problems other than a code the Foxwell was giving me - D7 IKE: Tank sensor 2 (without fuel pump), and Foxwell also said both sides were giving values that were too high; I never figured that one out):

Sender resistances with a pretty full tank:
Left: 481 Ohms.
Right: 474 Ohms

Voltage at disconnected plug to left sender:
12.0V

Voltages measured at the disconnected plug to the fuel pump assembly:
12.0V (going to the sensor)
13.0V (going to the fuel pump when activated; engine was off, battery charger on at 13.3V)

I think those can all be considered reasonably nominal values with a full tank.

So for example, if you were to unplug the connector and put a 100 Ohm resistor in place of where the sender would be, the fuel gauge should respond. High cluster readings from Test 6 should change as well, maybe not damped as the gauge will be.

[andrewwynn]

I've watched test six live with full sweep of the arms. There's instant and averages which will tell you if the reading is off due to smoothing.

I thought was nearly short circuit low and ≈ 450 Ω high. I could find the pictures I took when I fixed my weak wiper.