1985 Chevy El Camino starting car

Start at the battery and clean the connections. Even though they seem good sometimes they can be making little contact. Follow the wire to the to the starter to make sure you have voltage at the starter solenoid. The bigger wire then check the wire that goeas on the s terminal on the solenoid. Most times this is where the problem will be. Most times they are secured with a small nut. This wire does become frayed from vibrations and will break inside the shielding. Clean and replace this wire.