It just recently started to happen but when i go to fill my tank in my rx7, (its a 82 fb sacc or whatever) and it senses its full by making that clicking noise, but when i turn my car on and the fuel gauge says it only filled up half tank, my gauge works i know it, and when i tried to go past the click to fill it up more gas, it leaks a little in the back and stops when i turn on the car, but it will still read im at half tank, i have no clue why this is happening and hopefully it dosnt become a big problem, how could i solve this?

 

Sounds like It could be a bad sending unit or a bad check valve.
Do you know for sure that the tank IS Full?..If not then you may have to run it dry to see where the gauge is then fill up.(check tank capacity in specs.)

Obviously if it leaks (how?.you did not say how it leaks,.) you will have to delve into what the problem is and then take it from there.
I hate to say it but there are people that think that some car problems magically disappear if you wait long enough..But I know you are not one one them as you posted!

 

Im not quite sure if its full because when fill it up, it stops and the gauge shows it is at half tank, but when i drive it slowly goes down as it usually should, but if its one of those im definitely gonna check it out thanks!