1. Fuel Supply Issues:
* Fuel Pump: Is the fuel pump working? You should hear it prime when you turn the key on (before cranking). A weak or failed pump won't deliver enough fuel pressure. Check the fuel pressure at the rail with a gauge.
* Fuel Filter: A clogged fuel filter restricts fuel flow. Replace it as a preventative measure, especially if the vehicle is older.
* Fuel Lines: Check for kinks, cracks, or blockages in the fuel lines between the tank, pump, filter, and rail. A seemingly minor restriction can significantly impact fuel delivery.
* Fuel Pressure Regulator: A faulty fuel pressure regulator can either not maintain pressure or allow excessive pressure to escape. Again, a fuel pressure gauge is essential here.
* Low Fuel: Sounds obvious, but make sure the tank actually has enough fuel.
2. Injector Issues (Less Likely if Top End is Off):
* Injector Wiring: While unlikely since you've removed the top end, check for any damaged wiring harnesses to the injectors. A broken wire, loose connection, or short circuit will prevent them from operating.
* Injector Electrical Issues (ECU): Problems with the Engine Control Unit (ECU) or its communication with the injectors can prevent fuel delivery. This requires more advanced diagnostics.
* Clogged Injectors: Though less likely to be the primary cause in your situation, clogged injectors can restrict or prevent fuel flow. However, this is usually diagnosed *with* the engine running.
3. Other Potential Issues:
* Fuel Rail Pressure Sensor: A faulty sensor might send inaccurate readings to the ECU, leading to incorrect fuel delivery.
* Relay or Fuse: Check the fuse and relay associated with the fuel pump and injectors.
* Improper Reassembly: If you've recently done work on the top end, ensure everything is properly reassembled. A misplaced hose or sensor could disrupt the fuel system.
Troubleshooting Steps:
1. Check Fuel Pressure: This is the most important step. You absolutely need a fuel pressure gauge to test pressure at the fuel rail. This will quickly eliminate many potential issues.
2. Listen for Fuel Pump: Turn the key to the "on" position (don't crank). You should hear the fuel pump briefly activate.
3. Inspect Fuel Lines and Filter: Look for any visible damage or obstructions.
4. Check Injector Wiring: Inspect for damaged wiring or loose connections.
5. Consult a Repair Manual: A repair manual specific to your vehicle will provide detailed diagrams and troubleshooting steps for your fuel system.
6. Advanced Diagnostics: If you can't pinpoint the issue with basic checks, you might need a code reader or professional diagnostics to check for ECU errors.
Because you've removed the top half of the engine, some of the issues (like injector problems) are less likely, but the fuel *supply* is still crucial. Focus your attention on the fuel pump, filter, lines, pressure, and pressure regulator first. Using a fuel pressure gauge is critical for effective diagnosis.
