1996 Nissan Pathfinder Engine won't start

I have had the exact same problem. I finally started it by holding down the gas like you would an old chevy that's flooded. My fuel pump is only about 18 months old.

There are 3 things needed for an engine to run:
1. spark
2. fuel
3. compression

I doubt it's a compression problem unless you've recently overheated the engine. I would start with spark. Here's a video that explains how to check the ignition spark:
https://www.2carpros.com/car_repair_video/test_engine_ignition_system.htm
if you've got no spark, learn about the different parts of the ignition system, then work your way backwards from the spark plugs to the coil.

If you've got spark, then it may be a fuel problem. test the fuel pressure: https://www.2carpros.com/car_repair_video/test_fuel_injection_pressure.htm

If there's a fuel problem, start with the injectors and work your way back to the pump. Dont forget to check the fuel pump relay before condemning the pump.

If you've got fuel and spark then you may have a lack of engine compression. This indicates a serious internal engine problem. You can test the compression yourself but I wouldn't recommend an amatuer going any further than that. If you have no compression then take the car to a mechanic you trust.

To test the compression you will need a pressure gauge with a threaded fitting for inserting into a spark plug bore. You can get a compression gauge at most auto parts stores and it will have more detailed instructions with it. Make sure to remove the fuel pump relay first so the engine doesnt start while testing.