* Crankshaft Position Sensor (CKP): This sensor tells the computer the position of the crankshaft, which is crucial for timing the spark. A faulty CKP sensor will prevent spark. This is a very common cause of no-start issues.
* Cam Position Sensor (CMP): Similar to the CKP, but for the camshaft. A bad CMP will also prevent proper spark timing and lead to a no-start condition.
* Ignition Control Module (ICM): This module receives signals from the computer and controls the spark to the plugs. A failed ICM will result in no spark.
* Distributor (if equipped): While less common on later model vehicles like your 1997, some variations of the 5.7L Vortec might still use a distributor. A faulty distributor cap, rotor, or internal components can disrupt spark delivery. (Check your vehicle to confirm if it uses a distributor).
* Ignition Coil(s): These generate the high voltage needed for the spark. A bad coil(s) will prevent spark to the corresponding cylinder(s) or all cylinders if a single coil setup (coil-on-plug).
* PCM (Powertrain Control Module) / ECM (Engine Control Module): While less likely, a faulty PCM could be preventing spark signals. This is harder to diagnose and often requires professional help.
* Wiring Harness Issues: Despite having new wires, there might be a break or short in the main harness affecting the signal path to the ignition components.
Troubleshooting Steps:
1. Check for Spark: Use an inline spark tester or a spark plug boot tester on each spark plug wire one at a time while cranking the engine. This will definitively tell you if you have spark or not. No spark points strongly towards one of the above ignition system components.
2. Check CKP and CMP Sensors: These are relatively easy to access and test with a multimeter (check your vehicle's repair manual for specifics). Often, a simple visual inspection for damage or corrosion can reveal problems.
3. Inspect the ICM: Look for any signs of damage or overheating. While testing the ICM can be more complex, visual inspection is a good starting point.
4. Check the Ignition Coil(s): Visually inspect for cracks or damage. Advanced testing might involve checking resistance with a multimeter.
5. Fuel Pressure Test: Even though you mentioned ruling this out, double check fuel pressure. A low fuel pressure could mask a spark issue making it harder to diagnose.
If you are not comfortable working on your vehicle's electrical system, it is highly recommended you take it to a qualified mechanic for diagnosis and repair. Incorrectly diagnosing and repairing electrical issues can lead to further damage. Remember to always disconnect the negative battery terminal before working on any electrical components.
