Fuel gauge fault.

[ah]

My fuel gauge is doing strange things, when I put £20 of fuel in the gauge goes up to a quater full,drive down the road a mile, stop at the shop and when I restart the engine the gauge goes up over a quater - half full and then over a few miles it goes back down to quater full,now the needle has started slightly jumping around.

[Brianmoooore]

Not as strange as the petrol gauge on my E39 though, which, during a non stop 300+ mile run last week, went from just over half full, to the fuel light on, to absolutely empty.
Just as you'd expect, except that the whole run was on LPG as fuel, and I hadn't used a drop of petrol!
A quick turn of the ignition switch to "off", while still driving along, and then back to "start", and the gauge was back instantly to just over half. Weird!

Whatever is wrong with your E30, it won't be down to the same reasons, but first I need to know whether you have a 55 litre or 62 litre fuel tank, if it's the same size as the car was born with, and whether the instrument cluster is original.

[ah]

both totally original as car was born

[Brianmoooore]

but first I need to know whether you have a 55 litre or 62 litre fuel tank

[ah]

How do I find out the size Brian.

[TurtleDesignTech]

Don't mean to hijack the thread, but my car does something a bit similar at the moment and I am keen to hear Brian's answer.

Everytime the fuel gauge gets down to 1/2 full, it drops extremely quickly down to 1/4 full. Mine is a 55L tank with all original gauges. I did check the fuel float senders as per the wiki a while ago and they seemed fine.

Is is something to do with how fuel siphons into the right hand side of the tank as the amount of fuel gets lower. And one of the fuel senders being more sensitive than the other?

[HartgeH27]

Watching this one, interesting.