92 firebird current leak.

I have a 92 firebird with somekind of current leak.
the problem is, its not always.
sometimes I can put my battery in and after 2 weeks I can still start my car.
another time the battery is dead after 1 night. complete out of power.
now yesterday I was checking the car again, trying to get it running again. but looks like the fuel pressure unit is wasted.
so after a couple of times of trying to start the car.
I was hearing under the hood and every 2à secs or so I hear something ticking; ( like a hot echaust thats cooling of) or a heavy relay klikking in and out.
the sound is comming from the passenger side near the window, but downwards. its near the engine.
but the only relay I know there is the one on the starter.
could this be my problem? the starter relay or he starter itself?

if yes, what is it that makes it start klikking?