Fuel gauge

[Neathtvr]

Fitted new sender unit after tank was out of car for cleaning.
Refitted tank, connected electrics.
Put 3 gallons into tank, nothing showing on gauge.
Took sender out of tank, checked with resistance meter across terminals, there is a resistance reading with float at lowest and highest positions.
What and where do I check next to find fault?

[phillpot]

Put more fuel in?

Did you try the sender connected to the gauge while it was out the car?

Is the sender earthed to the tank and the tank to the chassis (or sender direct to chassis)?

[Neathtvr]

Put more fuel in, no change.
Wired a bulb direct from battery and checked Earth on tank, OK.
Stripped down plug connector to expose the black earth wire, checked this on bulb, OK.
Then joined the black earth wire to the green feed wire, gauge read as full. Therefore wiring and gauge OK.
Reassembled the wires back into the plug assembly and attached to sender unit, this has to be done carefully to make sure the wires connect with the sender unit pins.
Tested again, gauge now reads 1/3 full with approx 4 gallons.
Thanks for the help.