td5 defender fuel tank to pump seal?

i have recently upgraded to a td5 from my old 200 90. When i went to fill it up i found that it was leaking fuel from around the large plastic screw type cap that holds in the fuel pump/sender unit. The question is what is under this cap which seals it like an o ring etc?

large wide rubber ring which needs to be fitted to tank before pump/sender unit ,you might find knocking locking ring round with hammer and screw driver tightening it might stop the leak

cheers for that, investigated it tonight and found that someone has had the fuel pump out and pushed half the seal inside the tank and allowing it to leak. next question is can the fuel gauge/sensor be adjusted because at present it will go down to the yellow section and then runs out before the light comes on.

cheers for that, investigated it tonight and found that someone has had the fuel pump out and pushed half the seal inside the tank and allowing it to leak. next question is can the fuel gauge/sensor be adjusted because at present it will go down to the yellow section and then runs out before the light comes on.