Fuel gauge doesn’t work and sender unit has two earths no live even if I make one Earth with a tester probe the gauge still does not read anything
How do you mean it has two earths? Should have two terminals on it, one connected to the sender body. If you measure the resistance across the two with your meter, it should vary as the float is moved up and down.
Its now sadly often the case that fuel gauges have blackened crunchy resistance wire wrapped around the bimetallic element and will just fall apart internally after 40-50 years.. The sender resistance is only a few tens of ohms when it is working. So you need to use the 2000 ohm or 200 ohm range on a meter.
The sender does have two earths, one earths the case and the other earth runs to the gauge with variable ohms