I would check the injectors and see if they are clicking, put a screw driver to the injector the other end to your ear while cranking, and see if they are clicking if not the control unit could be bad, we replace a lot of ECM on the 2002 sentra This might be your problem, Thank You, XXXXX XXXXX know if you have any more questions, ROY!
For a new ECM the price is listed here, Thank You, XXXXX XXXXX know if you have any more questions, ROY!
If you have spark, injectors, check the fuel pressure ,if you had a gage to check pressure this would help should be around 35 psi. if that is ok unplug the air flow meter and see if it will start. also remove the spark plugs and see if they are fouled with fuel if they are clean them or replace them. If there is to much fuel in the cylinders remove the fuel pump fuse and crank it until it try to start, them reinstall the fuse. I have seen a lot of sentra become flooded and not start . try this and let me know, Thanks ROY!
I would replace the plugs, also check the oil for a fuel smell ,you might want to change the engine oil if it has fuel in it . what can happen is if the base idle is not set correctly the engine will not get enough air on cold start up , and load the plugs up. When you try to start the car hold the throttle open about a 1/4 open, to let more air in on cold start up this will also help from loading up plugs. Thank You, XXXXX XXXXX know if you have any more questions, ROY!