problems with my 1990 nissan 240sx ka24e

Ebay? If you hear nothing when you turn the key, start at the battery. Make sure it is producing 12+ volts. If you can't do it, remove the battery and have key a parts store check it. They'll do it for free. If it is good, then you need to have a helper turn the key to the start position while you check for power to the smaller wire on the starter. It should have 12+ volts. If it does, the starter is bad. If it doesn't, you need to check the starter relay. If good, then move to the ignition switch.

Let me know if you have questions.

Joe