ok so when i am driving along my fuel guage drops to 1/4 of a tank but when stopped with engine running it comes back up to were it is ment to be. any reason it would be doing this it use to work really well very accurate not now any idea y

Voltage stabilizer on back of speedo has had it. It feeds +10V to the gauge. Road vibrations make it give a lower voltage when it's knackered.
Mine did the same thing- the faster I went the lower it got, then you stopped and it came back up!!

Contact wombat on here for a new electronic one, his work good.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

i have tried 3 different ones and all do the same and 2 of them i no work in other minis

Well I bet they are all old ones, wombat's electronic ones are cheap.

It can't be much else with those symptoms.

I even ran mine up to 100kmh on a hoist, and it wouldn't do it-stayed steady as a rock. It's the road vibes that cause it.
So, I bought an electronic one and it fixed it..

The old ones work a bit like a blinker can, as they are just a bimetal strip, a vibrator.
1950s (or 40s) technology.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Could also have a hole / leak in the float on the sender making it near neutral buoyancy.

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I had the same thing coming back in the van from Melbourne on my Mini 50th Sydney trip,, i got to Seymour and all my gauges were reading like flag poles every second... made it an interesting drive back to QLD that night was a longgg night .... no fuel gauge or temp gauge,, but I knew she would pur back to QLD all good, just had to figure the fuel to km's ratio out by hand that is all

when i got back to QLD that morning, fitted a new one, and bobs your uncle, all good. didn't waste my time on a second hand one as they are all on their way out these days..

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Bluey-1973 Clubby - 1330, high lift, big cam, 7 port madness in progress..

Gumby-1978 Minivan, British Racing Green - 1310, high lift, mild cam, enlarged porting and chamber shape with big valve head, supercharged build in ever slow progress!