99Impreza

Check the voltage at the starter crank wire. It's the little wire on the starter solenoid. Have a budy check it while you turn the key to crank. Crank the key a couple of times to make sure. If you have voltage there consistently (it should be 12v) then check to see if you have excesive resistance in the wire from the battery to the starter solenoid and the battery connector to the battery terminal. If all that checks out you could need a new starter.