* Timing: Even with a new crank sensor (implied by replacing the ECM PROM), the timing could be off. The distributor's position, or even the distributor itself, could be faulty. Did you check the timing after installing everything? This is critical. A slightly off timing chain can prevent a start, even with spark and fuel.
* Camshaft Position Sensor (CMP Sensor): While you replaced the crank sensor (likely part of addressing the no start), the CMP sensor is equally important. A faulty one can prevent the engine from firing, even with proper fuel and spark.
* Faulty ECM (even with new PROM): The ECM itself might be faulty despite having a new PROM. It's possible there's a problem with the ECM's internal circuitry unrelated to the PROM. This is less likely after a comprehensive component replacement but still possible.
* Wiring harness issue: A short or break somewhere in the wiring harness could be interrupting the signal to the injectors or the ignition system. Check for damaged or corroded wires, especially those around the engine and related sensors.
* Injector issues (despite new injectors): Even new injectors can be faulty or improperly installed. Verify that they are all getting a signal and are spraying fuel correctly. A simple test would be to see if you get fuel spraying when cranking (potentially with injector removal to see spray). Be aware this is messy.
* Air intake system: Is the air intake system completely sealed? A leak in the intake system could cause a lean condition preventing starting.
* Compression: Low compression in one or more cylinders could still prevent the engine from firing, even with spark and fuel. A compression test is essential to rule this out.
Troubleshooting Steps:
1. Verify Timing: This is the most likely culprit at this point. Check your timing marks and ensure the distributor is correctly positioned. A professional mechanic with a timing light can easily confirm.
2. Check CMP Sensor: Replace or test the camshaft position sensor.
3. Perform a compression test: This will eliminate a crucial mechanical issue.
4. Inspect the wiring harness: Look for any damaged or corroded wires, paying close attention to the connections to the sensors, injectors, and coil packs.
5. Verify injector operation: Observe or test injector operation to see if they are actually spraying fuel.
6. Check for vacuum leaks: Inspect the entire intake system for leaks.
Important Note: You've replaced a significant number of parts. It's highly recommended that you seek the help of a qualified mechanic if you're not comfortable performing these diagnostic steps. Continuing to randomly replace parts without a proper diagnostic procedure can be expensive and time-consuming.
