It sounds like the solenoid is bad. With jumper cables, connect the positive cable to the top post on the solenoid. Connect the negative cable to the body of the starter. Now connect a volt meter as follows: connect the positive lead to the bottom post on the solenoid and connect the negative lead to the body of the starter. Now, using a screwdriver, jump 12V from the top post on the solenoid to the small post on the solenoid marked "S". You should see 12V on the volt meter. If not, the solenoid is bad.