Here's a systematic approach:
1. Verify Fuel Pressure:
* Accurate Measurement: Don't just rely on a visual gauge or a simple test. Use a fuel pressure gauge that's specifically designed for this application and connect it directly to the fuel rail. Your vehicle likely has a specific fuel pressure specification (check your owner's manual or a repair manual). It needs to reach this *and hold it* after the engine is cranked. A pressure that quickly drops indicates a leak somewhere in the system.
* Test Location: The test point is crucial. You want to measure pressure *at the fuel rail*, not just before the regulator. Improper placement can give misleading readings.
* Key Position: The pressure should build when the ignition is turned on (but the engine isn't running). There should be a noticeable increase in pressure.
2. Check for Clogged Injectors:
* Visual Inspection: Carefully remove the fuel injectors (after relieving pressure in the fuel system!). Inspect them for clogs or debris. Look closely at the spray nozzles. A simple visual inspection might reveal a problem.
* Injector Testing: The best way to know for sure if your injectors are functioning correctly is to have them professionally tested. An auto parts store or automotive repair shop can typically perform this test. This confirms spray pattern and flow rate. Don't just assume they're good because they're new; they could be faulty out of the box.
* In-Tank Filter: Is there a fuel filter within the gas tank? Some fuel systems have them. If so, this could also be restricting fuel flow.
3. Examine the Fuel Pump:
* Low Fuel Pressure: Even if you're getting *some* pressure, it might be insufficient. A weak fuel pump can still build some pressure but not enough to overcome injector resistance.
* Fuel Pump Relay: A faulty relay won't send power to the pump. Check the relay with a multimeter to make sure it's switching correctly.
* Fuel Pump Wiring: Inspect all wiring leading to and from the fuel pump for damage, shorts, or corrosion.
4. Investigate the PCM (Powertrain Control Module):
* PCM Fault: A malfunctioning PCM can prevent the injectors from firing. This is less likely if you've replaced other components, but it's still possible. A diagnostic scan code reader is necessary to check for PCM faults. The code might point directly to the fuel system or give clues about a related problem.
5. Check for Leaks:
* Visual Inspection: Inspect the entire fuel system for leaks—from the tank to the injectors. Look for wet spots, fuel odors, or signs of leaks. Pay close attention to the fuel lines and connections.
Important Safety Precautions:
* Fuel System Pressure: Always relieve pressure from the fuel system before working on it. Failure to do so can lead to serious injury.
* Flammability: Gasoline is highly flammable. Work in a well-ventilated area, away from open flames or sparks.
Next Steps:
1. Precise Fuel Pressure Test: Get an accurate fuel pressure reading at the rail. This is the most critical step.
2. Professional Injector Testing: Have your injectors tested professionally. It's the most reliable way to rule them out.
3. Diagnostic Scan: Have the vehicle scanned for trouble codes.
If you've done all this and still have no spray, you might need a professional mechanic to diagnose the problem. The combined factors could point to a more complex issue. Providing the results of these steps will help determine the next course of action.
