1995 nissan sentra won't start

It could be the fuel system.
It could either flooding or starving for fuel.
If injectors are fouled badly it will wet the plugs and not fire.
If plugs are pitted that makes it easier to flood. (check plug tip condition, check all plug wires and boots are good)

If it is starving -- fuel pump weak (going to fail).
Need to test fuel pump pressure.

I assume you checked the fuel pressure and it is normal.
Are the spark plugs getting spark when it fails to start ?
Are you getting injector pulse from the computer ?
Any trouble codes stored in the computer ?

Is there a check engine light on? Did car crank with old battery or you just replaced to see if would start?

I assume the pump was replaced because it was getting power but no fuel pressure ?
Are you still not getting fuel pressure ?
Spark to the plugs ?
Normal compression when cranking the engine ?
Security light not staying on ?

Can you hear the starter cranking the engine over?

Have you checked for spark?

Have you checked for fuel pressure?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

What is the pressure reading now with the electric fuel pump?

check fuel pump, fuel pump fuse, distributor,and ignition coil please. then you will need to check crank position sensor.(to do this you need to find factory service manual)

Pull off one of the plug wires and put a screwdriver in it, crank the engine and see if it is getting a spark. If so, pull off one of the fuel lines feeding the engine and check fuel pressure. If you are not getting fire, possible causes are: crankshaft sensor, ignition module, other causes I could determine after these are checked. Try to check these and if you need further help, I will help you as much as I can. If you are getting spark, and fuel, the main cause would be timing. Hope this helps

It could be a number of things. Have you tried to run any codes yet?

nissan is known for breaking timing belts