Well I suppose the off the cuff answer is they all behave strangely.
The gauge / DTE has been unpredictable since dropping below 1/4. DTE has been dropping sharply, as has teh gauge, but MPG has not been affected to anything like the extent required - I have been measuring an correlating over the past 150 miles.
I filled the car up today, for only the second time. Drove away from the pump, and noticed that the gauge was just above the reserve area, the light had gone off though.
Over the next 8 miles it gradually moved up to a bit under 3/4. After leaving in parked for 15 minutes it is now up to the white area at full.... but not above it which is what I expected from the other 9-5s.
Range increased from 56 miles before the fill to 103 miles, 248 miles and up to 550 miles when parked.
SID says 44 mpg after the fillup reset, so DTE should be ~720 miles. MPG increased progressively from 27 to 46 before dropping back due to the nature of the driving on the final bit.
Before I start getting stinky diesel everywhere, is this indicative of a sticking fuel indicator, or normal practice ?
Loosed and realign the sender unit, or remove and check for loose baffles ?
Do it now, or wait for the fuel level to drop again.
Filled the diesel up again today (yes, the tank lasted a month)
647 miles driven, 53 miles DTE and the low fuel light was on so a range of 690 miles. However, before filling up I checked the resistance on the fuel sender. It showed 100 ohms, which means 50 ohms worth of fuel or 10 litres......... DTE looks low by that measure. DTE and fuel gauge were dropping much faster than the mileage / sender unit resistances would indicate.
I filled up with 66 litres, which validates 10 litres remaining and a 75 litre tank. That works out at 44.6mpg, compared to SID which showed 43.6.
Last week I released and moved the sender unit, and lined up the alignment marks. When I restarted the car after filling up the gauge went straight up to full and DTE said 722 miles.
I drove 60 miles and read the resistance. 425 ohms, so a full tank after using about 6 litres. Just read it again at 122 miles. 409 ohms, but it's not quite on the level so I reckon that's really 400 ohms (I have been doing a lot of measurement) which would tie up pretty much exactly to the indicated 45 mpg.
In conclusion, the float is no longer sticking and the fuel level according to the sender seems good. Just a shame the needle tells lies :)
Maybe a Tech 2 session to adjust the offsets, along with another reseat of the sender unit as the top had diesel on it when I checked earlier today.
I've also seen some very strange fuel gauge behaviour recently, within a matter of a few miles it went from full to empty.
Motorway, 4th and 5th gear at a steady 60mph - 17.9mpg :o
It's a good job your car has the roof bar delete then :)
must have gained me at least 0.01mpg :D