1989 GMC Sierra won't turn over

Hello, I guess your saying, the starter won't crank? Make sure the battery has a full charge and all battery connections are clean and tight on both ends. Did you try cranking in neutral? The smaller wire at the starter solenoid, usually purple, should be hot with the key in the crank position. Is it? If not, backtrack the circuit, possibilities, faulty wiring circuit-- neutral switch-- ignition switch.