* Fuel Pump Relay: The fuel pump relay might be faulty, preventing power from reaching the new pump. This is a common and relatively inexpensive part to check.
* Clogged Fuel Filter (despite replacement): While the filter was replaced, there's a chance it wasn't done correctly, or there's a deeper clog further up the fuel line (e.g., in the tank itself). A clogged fuel tank pickup strainer is a possibility.
* Fuel Pressure Regulator: This component regulates the fuel pressure in the system. A failing regulator might not provide enough pressure, even with a new pump.
* Low Fuel Pressure Sensor: A faulty sensor might be sending incorrect signals to the engine control module (ECM), causing it to cut fuel.
* Fuel Injectors: Clogged or faulty fuel injectors could prevent sufficient fuel from reaching the combustion chambers.
* Wiring Issues: A problem with the wiring harness related to the fuel system (corrosion, breaks, short circuits) can prevent proper function even with new parts.
* Crankshaft Position Sensor (CKP): This sensor tells the ECM the engine's rotational position. A bad CKP can cause intermittent starting and running problems that *appear* to be fuel related.
* Mass Airflow Sensor (MAF): A faulty MAF sensor provides inaccurate air measurements to the ECM, leading to improper fuel/air mixture calculations, causing poor running or stalling.
* Engine Control Module (ECM): Though less likely, a failing ECM could be misinterpreting sensor data or issuing incorrect commands. This is generally diagnosed last.
Troubleshooting Steps:
1. Check fuel pressure: This is crucial. A mechanic needs a fuel pressure gauge to measure the pressure at the fuel rail. This will tell if the pump is delivering adequate pressure.
2. Inspect the fuel lines and connections: Look for any leaks, cracks, or kinks in the fuel lines.
3. Test the fuel pump relay: This is a simple test that can be done with a multimeter.
4. Check the fuel pump fuse: Another easy check to rule out a blown fuse.
5. Inspect the fuel filter (again!): Make sure it was installed correctly and is not clogged (maybe a speck of debris got in it during replacement).
6. Scan for trouble codes: Use an OBD-II scanner to check for any diagnostic trouble codes (DTCs) stored in the ECM. This will point toward specific areas of concern.
Without more information about the vehicle's behavior (e.g., when it dies, does the engine crank, are there any warning lights on?), it's difficult to pinpoint the exact cause. A professional mechanic is the best resource for diagnosis and repair.
