* Crank Position Sensor (CKP): A faulty CKP sensor prevents the engine from receiving the correct timing signal, leading to sputtering and failure to start. This is a common cause when a car *almost* starts. It's relatively inexpensive to replace.
* Cam Position Sensor (CMP): Similar to the CKP, a bad CMP sensor disrupts timing, resulting in a no-start or rough running condition.
* Ignition Coil(s): While you have spark, the spark might be weak or inconsistent. A failing ignition coil can cause misfires and difficulty starting. Test each coil individually if possible.
* MAF Sensor (Mass Airflow Sensor): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can send incorrect information to the computer, leading to a lean or rich fuel mixture, resulting in starting problems. Try cleaning it with MAF sensor cleaner first.
* Throttle Position Sensor (TPS): An inaccurate TPS reading can prevent proper fuel delivery and ignition timing.
* Air intake leak: A leak after the MAF sensor will throw off the air/fuel mixture. Check all connections and the air intake hose for cracks or loose clamps.
* Fuel pressure regulator: Although you have fuel at the plugs, the fuel pressure regulator might be malfunctioning, delivering insufficient pressure. This is less likely given fuel is reaching the plugs, but it's possible.
* Computer/ECM Issues: Though less common, a problem with the engine control module could be the culprit. This would require professional diagnosis.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any trouble codes stored in the vehicle's computer. This will often point directly to the problem.
2. Check Fuel Pressure: Even though you see fuel on the plugs, accurately measure fuel pressure using a fuel pressure gauge. This confirms adequate pressure is reaching the injectors.
3. Inspect and Clean the MAF Sensor: Clean the MAF sensor with MAF sensor cleaner (available at auto parts stores). Follow the instructions carefully.
4. Test the Spark: While you mentioned spark, ensure it's strong enough. A weak spark can still result in a sputtering start. A spark tester will confirm the strength of the spark.
5. Check for Vacuum Leaks: Inspect all vacuum hoses for cracks or leaks. A large leak will prevent proper engine operation.
6. Start with the cheapest and easiest: Begin by checking the CKP sensor, cleaning the MAF sensor, and checking for vacuum leaks. These are relatively simple fixes and are common causes of similar symptoms.
If you're not comfortable working on the vehicle yourself, take it to a qualified mechanic for diagnosis. Providing them with the information that you've already replaced the fuel pump, and have spark and fuel reaching the plugs, will speed up the diagnostic process.
