Fuel gauge playing up

[Goldensyrup]

My fuel gauge was working before she tucked away for winter and now it's only showing empty ( gauge moves from below empty to empty ) .
We had to have my engine out to change the clutch this weekend so thought we'd have a look at the sender unit. It's not the original one so has recently been changed before my ownership. We tested it and worked fine when and was showing movement on the gauge.
Swapped clutch and put everything back in and it's stopped working again?

 

[subheatadey]

If you had the firewall out to check the fuel gauge did you connect the earth up?

 

[Goldensyrup]

Yeah earth was connected back properly, apparently it could be the float sticking in the unit when it's in the petrol. It worked out of the tank just not inside it