Yes.Unfortunately,one has to insert it into the tank.Weird rules but i have to follow them. 
And yeah,the sensor is working now, used aluminium tape. but the resolution is really crappy.
full tank- output is fluctuating between 5000-6000, which is ok.i can use constrain function later.
half tank- nothing yet,same values. :~
quarter tank - now some change,show about 4000-4500 now.
almost empty-suddenly decreases from 4000 to about 300,the 150 and then 30-40...which is ur capacitance between 2 metal plates with air as an dielectric.
how can i increase the resolution?...should i increase the taping?...or increase the timeout value?
this is almost same as my fuel tank:
Briggs and stratton fuel tank.