1993 Nissan 300ZX car randomly won't start

We first need to find out what is missing on start up. Spark, fuel pressure, or both. This will help us narrow down the problem. Without this info, we are just guessing, and guessing can get expensive for you. Things you can check are fuel filter, when the last tune up was done, etc. Please advise.

You check the filter by blowing through it in the same direction the fuel flows. It should blow through fairly easily. Being careful not to get a mouthful of gas. To test the fuel pressure, you need an adapter with a guage that fits between the fuel regulator and the fuel rail. You will also want to check for injector pulse with an "incandescent" test light, or an analog volt meter.

OK, If you have fuel to the fuel rail, and spark at the plugs, the next step is pulse at the fuel injectors. You can do this with a test light at an injector connector. As you crank the engine the light will blink as the ECM fires the injector circuit. One terminal should be constant hot to ground with the key on. The ECM grounds the other terminal to pulse the injector. Let me know what you find.