1. Verify Fuel Delivery:
* Fuel Pressure: This is CRUCIAL. You need a fuel pressure gauge to check the pressure at the fuel rail. The specifications for your engine should be in your owner's manual or readily available online. Low or no pressure indicates a problem *even if* you replaced the pump and filter. There might be a blockage in the line, a faulty fuel pressure regulator, or a problem with the fuel pump's wiring/connections.
* Visual Fuel Inspection: With the fuel pressure gauge attached, have someone crank the engine. Look for fuel spraying from the injectors. If no fuel is spraying, you have a fuel delivery problem. Even if some fuel is spraying it may not be sufficient. Low pressure can lead to a no-start.
2. Verify Spark:
* Spark Test: Use a spark tester or even a good quality spark plug wire and a grounded metal object to check for spark at each spark plug wire. Crank the engine while observing. Weak or no spark points to a problem within the ignition system, despite your replacements. Possible culprits (even after replacement):
* Ignition Control Module (ICM): Though you replaced it, ensure it's properly seated and grounded. A faulty ICM is still possible, even with a new one. (Check for a bad ground).
* Distributor Cap and Rotor: While you replaced them, ensure they are properly installed and that there are no cracks or damage.
* Wiring: Check all the wiring related to the ignition system for breaks, shorts, or corrosion. This includes the wiring to the crank position sensor (if equipped).
* Crank Position Sensor (CKP): This sensor tells the ignition system when to fire the spark plugs. A faulty CKP can prevent starting.
3. Check Sensors:
* Crankshaft Position Sensor (CKP): (As mentioned above) This is critical for ignition timing. A bad CKP will cause no start. It's often overlooked, and even a new ICM won't help if the CPK is bad.
* Cam Position Sensor (CMP): (If equipped) Similar to the CKP, but for the camshaft. A faulty CMP will often cause misfires or no start.
* Mass Airflow Sensor (MAF): A faulty MAF sensor can cause a lean condition, resulting in a no-start or rough running.
4. Other Possibilities:
* Security System: Does your truck have an anti-theft system? A malfunctioning immobilizer could prevent the engine from starting even if everything else is working.
* Wiring Harnesses: A bad ground wire or a shorted wire in the main harness can cause a wide variety of problems, and might be worth checking.
Systematic Troubleshooting:
Work through these points methodically. Don't jump to replacing more parts until you've verified the basics. Using a multimeter to check voltage and continuity at various points in the fuel and ignition systems will be extremely helpful. A fuel pressure gauge is almost indispensable for diagnosing fuel delivery problems.
If you've verified fuel pressure and spark and still have no start, consider getting a professional mechanic to diagnose the problem. They have the tools and experience to quickly pinpoint the issue you may be missing.
