1985 Nissan 300ZX Cold starting

Check the fuel pressure and comeback with your readings or you can try below and see what happens when it cranks and refuses to start

Get a carb cleaner and spray into the carb or the throttle body on an EFI. Did it start and die? If not disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel problem, check the fuel pressure to rule out the fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil, distributor pick-up coil, ignition control module, cam and crank sensors-

Fuel pressure at idle should be 30psi and when accelerator is depressed should be 37psi

Noid light is what you use to check if the injector/s are pulsing-meaning getting power on and off

Let me know about the snapping blue spark-nonexistence it will never start