1. Verify the New Fuel Pump Installation:
* Proper Connection: Double-check all electrical connections to the fuel pump. A loose or corroded connection is a common culprit. Ensure the ground is solid.
* Fuel Pump Relay: If your vehicle uses a fuel pump relay, test it or swap it with a known good relay (if you have a spare). A faulty relay won't power the pump.
* Fuel Pump Fuse: Check the fuel pump fuse in your fuse box. A blown fuse will prevent the pump from working.
* In-Tank Sender Unit (if applicable): If the fuel pump is part of an in-tank module (common in many cars), the problem might be with other components in that module, not just the pump itself.
* Pressure Test: The most definitive check. Use a fuel pressure gauge to measure the fuel pressure at the fuel rail. This tells you if the pump is actually delivering fuel. A low or no reading indicates a problem *beyond* the pump.
2. Beyond the Fuel Pump:
* Ignition System:
* Spark Plugs: Check their condition. Are they worn, fouled, or damaged?
* Spark Plug Wires: Inspect for cracks, damage, or loose connections.
* Ignition Coil: Ensure it's functioning correctly. A faulty coil will prevent spark.
* Distributor (if applicable): Older vehicles use distributors; check the cap, rotor, and points for wear or damage.
* Cranking Speed: Is the engine cranking over quickly or slowly? A slow crank might indicate a weak battery, faulty starter, or other starting system issue.
* Fuel Delivery System (Beyond the Pump):
* Fuel Filter: A clogged fuel filter can restrict fuel flow even with a new pump. Replace it.
* Fuel Injectors: Faulty injectors can prevent fuel from reaching the cylinders. They might need cleaning or replacement. A fuel pressure test will often reveal issues here.
* Computer System:
* Crankshaft Position Sensor (CKP): A faulty CKP sensor won't allow the engine to start.
* Cam Position Sensor (CMP): Similar to the CKP, a bad CMP sensor will prevent starting.
* Other Sensors: Numerous other sensors contribute to the engine's ability to start. A diagnostic scan tool can check for error codes.
* Immobilizer System: Some cars have an immobilizer that prevents starting if it doesn't recognize the key.
3. Getting Help:
* Diagnostic Scan Tool: A scan tool can read diagnostic trouble codes (DTCs) stored in your vehicle's computer. This can pinpoint the problem area.
* Mechanic: If you're not comfortable troubleshooting these issues yourself, take your vehicle to a qualified mechanic for diagnosis and repair. Trying to troubleshoot without the proper tools and knowledge can lead to further damage.
Before you do anything, make sure the battery is fully charged and the terminals are clean and tight. A low battery can mimic many starting problems. Remember safety first – work on your vehicle in a well-ventilated area and disconnect the battery's negative terminal before working on the electrical system.
