You have to verify that you have sufficient fuel pressure - 34PSI with engine running and 43PSI with engine OFF (Ignition ON). You need to connect a fuel pressure gauge (T-fitting) between fuel filter and fuel rail.
Just a basic check - turn Ignition Switch to ON for at least 5 seconds to allow the pump to run at full pressure ( @ 43PSI) then START the car. If the car starts, you have low fuel pressure due to failing pump or dirty fuel filter.
Check the Crankshaft Position (POS) sensor and related harness going into the ECM. You may also have a loose/dirty connection on the ECM. You can wiggle the main engine harness while somebody else tries to start the car to see if you have a loose connection there. You might as well check the Camshaft position sensor. It's possible that you have a bad ECM.
Here's the link to the FSM:
http://www.nicoclub.com/FSM/maxima/1995/ec.pdf