* Insufficient Fuel Delivery: While you have fuel *pressure*, that doesn't guarantee sufficient fuel *flow*. A clogged fuel filter, a faulty fuel pump (even with pressure, it might not be delivering enough volume), or issues within the fuel injectors themselves could prevent adequate fuel from reaching the combustion chamber. A fuel pressure *gauge* connected directly to the fuel rail would be helpful to confirm pressure *during* cranking. Static pressure is different from dynamic pressure under cranking conditions.
* Timing Issues: The distributor could be slightly out of time, leading to improper ignition timing. A faulty crankshaft position sensor (CKP sensor) or camshaft position sensor (CMP sensor) on these cars can prevent proper ignition timing and fuel injection timing. The computer relies heavily on these sensors.
* Ignition System Problems: Even with spark, the spark may be weak, insufficient, or improperly timed to each cylinder. Worn or faulty spark plug wires, weak ignition coil, or problems with the ignition control module (ICM) could be to blame.
* Computer/Sensor Problems: The Throttle Position Sensor (TPS), Mass Airflow Sensor (MAF sensor if equipped - some '89s had MAF, others still used a MAP sensor), or other sensors feeding the ECM (Engine Control Module) could be sending incorrect signals, preventing proper fuel/air mixture and ignition timing. A failing ECM is also a possibility, though less common.
* Vacuum Leaks: Large vacuum leaks can disrupt the fuel and ignition system's operation. A thorough inspection of all vacuum lines is necessary.
* Compression Issues: Low compression in one or more cylinders would prevent proper combustion, even with fuel and spark. A compression test is crucial to rule this out.
* Clogged Catalytic Converter: While less likely to prevent starting completely, a severely clogged catalytic converter can restrict exhaust flow enough to make starting difficult.
Troubleshooting Steps:
1. Verify Fuel Delivery During Cranking: Connect a fuel pressure gauge to monitor pressure while cranking. Low or fluctuating pressure indicates a problem with the fuel pump or injectors. Also, listen closely near the fuel rail for the "clicking" sound of the injectors firing.
2. Check Spark Strength: Use a spark tester to confirm strong spark at each spark plug. Pay attention to the color and consistency of the spark.
3. Inspect Vacuum Lines: Look for any cracks, leaks, or loose connections in the vacuum lines.
4. Test Sensors: Use a multimeter to check the voltage and resistance of key sensors (TPS, MAF/MAP, CKP, CMP). These often require a specific procedure for testing.
5. Compression Test: Perform a compression test to assess the health of the engine's cylinders.
6. Check for Codes: Use an OBDI scanner (if available for this model year) to read any diagnostic trouble codes stored in the ECM.
Addressing these potential issues systematically is the best approach to diagnose why your IROC-Z won't start. Consider consulting a repair manual specific to your 1989 Camaro IROC-Z 350 TPI for detailed troubleshooting information and diagnostic procedures.
