My 1988 nissan d21 4x4 (hardbody) wouldn’t start either. I had to do many things: replace starter, cleanup & rewire fusible links and replace ignition switch. After cleaned up my fusible link (major problem with these trucks) and probably where your problem is…putting in the key and turn to ON, I could hear the fuel pump going. When I turned the ignition to start, there was just a click and then all the electrical would go off. All the panel red lights and fuel guage would just die. Turning the ignition to start again would do nothing. Then I take the key out and reinsert, I could get the normal start up panel lights to turn on, but further turning to start would end up the same with everything cutting out. I lastly then replaced the ignition switch ($30) and truck started.