1994 Nissan Sentra car sometimes starts

If its cranking over and refuses to start-check for fuel and spark

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 related problem, check the fuel pressure to rule out the fuel filter/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 packs,coil's resistances,cap and rotor /distributor pick-up coil, ignition control module, ECM,Ignitor cam and crank sensors- Note: If it doesn't apply disregard it

The car is not cranking over. It would click. We replaced the starter. It started for 3 days, now it won't crank at all. We thought at this point it was the battery, although all the lights worked. Battery is new only 5 months old. Any idea what it could be? We did bring it to a repair shop, and it started eveytime he tried for about 2 days. Said there was nothing wrong. It ran for about a week, and now didn't start.

Load test both the battery & alternator if okay inspect and test the clutch interlock relay and clutch interlock switch and double check wiring connections