Sentra not starting

I have a 2000 Nissan sentra and I have times when I will drive for couple days and then it won’t start it will just crank over and over but won’t fire I have had it to several people but no answer replaced the fuel pump relay switch but nothing I need help

Has anyone checked for engine trouble codes?

Yes but nothing

It needs to be diagnosed in failure mode. If you can figure out how to replicate the problem on a consistent basis to have it analyzed in failure mode would be the best. Is the maintenance for fuel filter up to date? does it happen on damp or rainy days?

Just random times fuel pump and relay switch have been replaced

The problem might be with the crankshaft position sensor.

http://www.rockauto.com/catalog/moreinfo.php?pk=2413230&cc=1429501

As you can see the thing is made of plastic.

If the computer doesn’t see a signal from this sensor, the computer see’s no reason to operate the ignition and the fuel injection system. So the engine doesn’t start

Tester