1. Verify the Installation:
* Fuel Pump Installation: Did you install the new fuel pump correctly? A common mistake is incorrect orientation or not seating it properly. A faulty connection within the tank can also prevent it from working. Check all connections and ensure the pump is properly grounded. Did you prime the pump before attempting to start? Some pumps require this. Consult your repair manual for the specific procedure.
* Pressure Regulator Installation: Ensure the regulator is correctly seated and the vacuum line is properly connected. A leak in the vacuum line can affect fuel pressure.
* Fuel Filter: Did you replace the fuel filter? A clogged filter can prevent fuel from reaching the engine even with a new pump. This is a cheap and easy thing to check.
* Wiring: Double-check all wiring connections to the fuel pump and pressure regulator. Look for any damaged wires, loose connections, or corrosion. A simple wiring fault is a common oversight.
2. Check for Fuel Pressure:
* Using a Fuel Pressure Gauge: This is crucial. You need to measure the fuel pressure at the fuel rail. The pressure should be within the specifications listed in your owner's manual or a repair manual for your specific engine. Low or no pressure indicates a problem even after replacing the pump and regulator. This pressure reading will help pinpoint the issue.
3. Other Potential Issues:
* Cranking but Not Starting: If the engine cranks (turns over) but doesn't start, the problem isn't necessarily fuel-related. Consider:
* Spark Plugs: Check for spark at the spark plugs. Weak or faulty spark plugs can prevent ignition.
* Ignition Coil: A faulty ignition coil can also prevent sparking.
* Ignition System Components: Issues with the distributor (if equipped), crankshaft position sensor, camshaft position sensor, or other ignition components can hinder starting.
* Computer Issues (PCM): A malfunctioning Powertrain Control Module (PCM) can prevent fuel delivery or ignition. This is less likely but possible.
* No Cranking: If the engine doesn't even crank, the problem is likely in the battery, starter, or related wiring.
* Immobilizer System: Some vehicles have immobilizer systems that prevent starting unless the correct key is used. Ensure you have the correct key.
* Fuel Injector Issues: While less common, clogged or faulty fuel injectors can prevent fuel from entering the combustion chamber.
4. Seek Professional Help:
If you've checked all of the above and still can't identify the problem, it's best to take your vehicle to a qualified mechanic. They have the tools and expertise to diagnose the issue more accurately. A fuel pressure gauge test is the most critical next step if you haven't performed that already.
Remember safety first! Work in a well-ventilated area when dealing with fuel systems. Always disconnect the negative battery terminal before working on any electrical components.
