Hyundai Repair: Wont start, crankshaft position sensor, hyundai elantra

Question
Hi i have a 2001 Hyundai Elantra and it was playing turn its self off all the time i since replaced the fuel filter and now the car doesn't start but it is getting fuel to the fuel rail but is not going any further so i doesn't have an injector pulse how could i fix this...
thanks

Answer
If you have no injector pulse, this suggests that either the engine control module (ECM) isn't seeing the necessary signal (crankshaft position sensor) to determine when to fire the injectors, the ECM isn't powering up, or the ECM isn't operating properly.

First, check to see whether the check engine lamp illuminates when the ignition is turned to the "on" position (engine stopped).  If so, you've just verified the ECM powers up.  While not concrete, it's also a reasonable indicator that the ECM is functional.  

To check the crankshaft position sensor, you'll need an oscilloscope (which I presume you don't have).  If you have access to a code reader or scan tool, you might also check the ECM for trouble codes.  If a crank sensor code is present, it's a safe bet the problem is with the sensor.  Even if you don't have any specific information to this effect, if the check engine lamp illuminates, I'd still recommend replacing the crankshaft position sensor as a try.  Often they fail intermittently when hot, causing exactly the symptoms you describe.