If your car is getting fuel (you've confirmed this by replacing the injectors) and still won't start, the problem lies elsewhere in the starting system or the ignition system. Here are some more likely culprits:
* Spark Plugs/Wires: Inspect the spark plugs for fouling, damage, or wear. Check the spark plug wires for cracks or damage. A simple test involves pulling a plug wire, holding the end near the engine block (being careful not to touch the metal), and cranking the engine. You should see a strong spark. If not, there's a problem with the ignition system.
* Ignition Coil(s): The ignition coil(s) provide the high voltage needed to create the spark. These can fail and prevent starting. A mechanic or an advanced scan tool might be needed to test the coils reliably.
* Crankshaft Position Sensor (CKP) or Camshaft Position Sensor (CMP): These sensors tell the computer the engine's rotational position, which is critical for precisely timed fuel injection and spark. A faulty sensor will prevent the engine from starting. These typically require a scan tool to diagnose properly.
* Fuel Pump (despite injector replacement): While you've replaced injectors, ensure the fuel pump is actually delivering fuel at sufficient pressure. A low fuel pressure, even with good injectors, will prevent starting. A fuel pressure gauge is needed to check this.
* Computer/ECU Problems: Though less common, a problem with the Engine Control Unit (ECU) can prevent the engine from starting. This usually requires specialized diagnostic tools.
* Timing Belt/Chain: A broken or severely slipped timing belt or chain will prevent the engine from starting. This is a more serious mechanical issue.
How to *rule out* the catalytic converter:
Since a bad catalytic converter won't prevent starting, you don't need to test it specifically at this stage. Focus on the ignition and fuel delivery systems as outlined above. If you've gone through those checks and still have no start, *then* you could start looking at more complex issues. A mechanic with a scan tool is your best bet at this point. They can check for diagnostic trouble codes (DTCs) which can pinpoint the problem far more efficiently than trial-and-error testing.
