1. Power and Ground to the Injectors:
* Check for Power: With the ignition ON (engine OFF), use a test light or multimeter to check for battery voltage (+12V) at the injector connector(s). You should have power at one wire on each injector connector. If no power, trace the power wire back towards the ECM. A blown fuse or faulty relay is a possibility.
* Check for Ground: Test for a good ground connection at the other wire of each injector connector. A poor ground connection will prevent the injectors from firing.
2. Injector Signal Wire:
* Continuity Test: This requires a wiring diagram for your specific year and model. The injector signal wires are controlled by the ECM. Using a multimeter, check the continuity from the ECM connector to each injector connector. Look for broken, corroded, or disconnected wires in this circuit.
* Signal Wire Voltage: With the ignition ON, you should see a square-wave pulse signal on the injector control wire (when cranking). You'll need a multimeter capable of capturing this or an oscilloscope for a definitive reading. A lack of this signal indicates a problem either in the ECM (unlikely given no codes) or in the wiring to the injectors.
3. ECM Power and Ground:
* Check ECM Power and Ground: Ensure the ECM itself is receiving proper power and ground. Locate the ECM's power and ground connections and test them.
4. Crankshaft Position Sensor (CKP):
* A faulty CKP sensor can prevent the ECM from providing the injector pulse. While the engine might crank, the ECM needs the CKP signal to know where the engine is in its cycle to properly time the fuel injection. Test its resistance and voltage according to the factory specifications in your repair manual.
5. Ignition Control Module (ICM): (If your system has one - some TBI systems integrate this function into the ECM)
* A malfunctioning ICM can prevent the spark and in some cases interfere with fuel injection. If applicable, test the ICM according to your repair manual's specifications.
6. Pinched or Damaged Wiring Harnesses:
* Carefully inspect the wiring harnesses leading to and from the ECM and injectors for any signs of damage, chafing, or pinching.
Important Considerations:
* Repair Manual: A factory repair manual is invaluable. It contains wiring diagrams, component specifications, and troubleshooting guides specific to your vehicle.
* Test Light vs. Multimeter: A test light is useful for checking for power, but a multimeter provides far more precise measurements for continuity, voltage, and resistance.
* Professional Help: If you're not comfortable working with automotive electrical systems, consider seeking professional help from a mechanic. Improper troubleshooting can cause further damage.
By systematically checking these areas, you should be able to isolate the cause of the fuel injector problem. Remember safety first—disconnect the battery negative terminal before working on the electrical system.
