1995 nissan240sx wont start I replaced the starter it still wont start unless I push it what could be the cause?

A no start condition can be caused by a bad battery, bad connections on the battery, bad connections on the starter or ground and possibly by a bad neutral safety switch or ignition switch. Use a test light and see if your getting fire to the small wire on the starter when someone trys to start it. If you are, the starter is not working. If you aren't, check the ignition switch and the safety switch.