maniac240sx_7

ok ive looked and looked and looked.. im finding nothing that helps me. I never turn to forums unless im stuck. IM STUCK!!!
problem.
my 1990 s13 240sx with a KA24DE will not start wont even turn over. this problem has came out of the blue. car started a few times last spring then died. then noticed my dash lights were staying on along with my tail lights. so i would unplug my battery. so my guess is i have a drawl somewhere.. still the car should get power to the engine..? so for the past few months ive had time to work on it and have got no where.
i turn my key everything inside the car turns on properly.(fuel,lights,and the dinging). so i turn my key all the way over and crack!! all my power is gone. sometimes it will just click but when it goes crack!! kills everything and i have to wait awhile for the power to come back.??
does anyone have any answers for me or what i should be looking for?
thanks for reading and the help will be very grateful!!!