1. Power and Ground:
* Fuel Pump Relay: Ensure the fuel pump relay is functioning correctly. A faulty relay will prevent the pump from running, leading to no fuel pressure and subsequently, no injector pulse (as the system may detect a lack of fuel). Test the relay by swapping it with a known good one.
* Power to the Fuel Injectors: Verify that the injectors receive power (check the voltage at the injector connector). A blown fuse or a wiring problem could be the culprit.
* Grounds: Check for clean and secure ground connections throughout the fuel injection system. Corrosion can disrupt electrical signals.
2. Engine Control Module (ECM) / Computer:
* ECM Failure: The ECM controls the injector pulse. A faulty ECM is a possibility, but this is usually a last resort diagnosis as it's expensive to replace.
* ECM Programming: While less common, there might be an issue with the ECM's programming or calibration. This is a specialized area requiring diagnostic equipment.
3. Crankshaft Position Sensor (CKP):
* CKP Sensor Failure: This sensor tells the ECM the position of the crankshaft. Without this information, the ECM won't know when to fire the injectors. A faulty sensor will prevent injection.
* CKP Sensor Wiring: Inspect the wiring harness to the CKP sensor for damage, shorts, or poor connections.
4. Other Sensors:
* Throttle Position Sensor (TPS): A faulty TPS can cause the ECM to not signal the injectors.
* Air Flow Meter (AFM) (or MAP Sensor depending on specific configuration): Problems with airflow measurement can also cause the ECM to withhold injector pulses.
* Oxygen Sensor (O2 Sensor): Although less directly involved in the immediate injector pulse, a malfunctioning O2 sensor can affect the fuel mixture calculations and result in the ECM shutting down the injectors.
5. Ignition System: While you're specifically saying *no* injector pulse, a problem in the ignition system *might* indirectly prevent the injectors from firing, though the symptom wouldn't be obvious. Check for:
* Distributor (if it's not truly a DIS system): If it is an older DIS-modified system, problems with the distributor could also impact the system. It's highly unlikely with a true distributorless system.
* Ignition Coil: A failing coil (though rare, it does happen) could lead to cascading problems.
Troubleshooting Steps:
1. Start with the basics: Check fuses, relays, and all wiring connections. Look for any obvious signs of damage or corrosion.
2. Use a multimeter: Measure voltage and ground at the injector connectors and various sensors. Follow a wiring diagram for your specific year and engine to track down the wiring.
3. Consult a wiring diagram: A detailed wiring diagram is indispensable for tracing signals and locating components.
4. OBD I Scanner (optional): A scan tool compatible with the OBD-I system in your vehicle will be able to retrieve trouble codes that may point towards the faulty component. These can provide a huge amount of direction, especially if there is an intermittent problem.
5. Professional Diagnosis: If you are not comfortable working with automotive electrical systems, consider taking it to a qualified mechanic.
Remember safety first! Disconnect the negative battery terminal before working on the electrical system. Working on fuel injection systems involves working with gasoline - be extremely careful.
