Fuel gauge not working
 

Long story short guys - battery on my S8 went flat.

Took it out, charged it & put it back in and now the fuel gauge ain't working.

I did have a new fuel pump installed a couple months ago, and everything has been fine since.
As well as that, there's about 1/4 tank of fuel in the car BUT my driveway is on an angle - would this make any differences when the battery is changed?

I'd start with simple stuff first, Have you tried placing it onto a level area and seeing if it responds? Or adding a small amount of fuel to see if it reads then? I could be wrong but as far as i know I can't see how changing the battery could affect it, the gauge only reads when the ignition is on?! I know my gauge has a reasonably slow response at low levels (just above when the warning comes on) I can park on a slope with it saying all is well, start next time with it saying its thirsty and after a few minutes drive on the level, the warning goes off again.

I would have said there is nothing in charging the battery and fuel gauge. You did take the battery out the car when charging tho, right?

There is a fuel sender on the right hand side of the tank (when stood at the rear looking in) under the carpet 4 screws hold down a access panel, whip it off and just check connectors, after checking the fuse.

Also find that when parked facing up hill the gauge says there is more fuel than when parked level or nose down.

Yes, I too find the fuel guage quite variable, though predictably so. It's very similar on my newer S8 to the old one, so maybe a design "feature". :D

Slopes affect it, but especially first thing on a cold day it seriously under-reads.
For example, on Saturday night as I got home the gauge was "lowish" and reported range was 40 miles. I knew that the next day I was going on a journey that would pass one of my regular Shell "watering holes" within a very few miles so no concerns.

But starting off on Sunday the gauge showed empty and range zero. I ignored it and drove just over 10 miles to reach a convenient Shell station on the route.

I squeezed in about 76 litres, brimming the pipe, so it still had nearly 3 gallons left when I'd arrived, more when I left home! :tuttut:

Don't forget that when warming the valve timing is adjusted so exhaulst gasses are still burning when going down the pipes to warm cat's up, so the range would not be far but as it warms but will increase. I'd be very supprised if the gauge moved at all tho.

Thanks for the tips guys, it seems to have righted itself once i stuck more fuel in it (well i think so - either that or its now reading 1/4 tank under how much fuek is in it. Either way, i dont run it low if i can help it.