Fuel System:
* No Fuel: Empty tank (obvious but worth checking!), fuel pump failure (no pressure to injectors), clogged fuel filter, faulty fuel pump relay, or problems within the fuel injectors themselves.
* Low Fuel Pressure: The fuel pump may be weak, delivering insufficient pressure to atomize the fuel properly. This can be tested with a fuel pressure gauge.
* Clogged Fuel Injectors: Dirty or clogged injectors prevent proper fuel delivery. This is common in older vehicles.
Ignition System:
* Spark Plugs: Worn, fouled, or damaged spark plugs are a very common cause. Check their condition and gap.
* Spark Plug Wires: Damaged, cracked, or loose wires can prevent spark from reaching the plugs. Inspect for damage and ensure secure connections.
* Ignition Coil: The coil provides high voltage to the spark plugs. A faulty coil will prevent sparking.
* Distributor Cap and Rotor (if applicable): These components distribute the high voltage to the spark plugs. Cracks or corrosion can interrupt the spark. (Note: Some 1996 Explorers may have a distributor, others might use a coil-on-plug system.)
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position, essential for proper ignition timing. A faulty CKP will prevent the engine from starting.
* Cam Position Sensor (CMP): Similar to the CKP, but for the camshaft. A faulty CMP can prevent starting.
* Ignition Control Module (ICM): This module controls the ignition system. A faulty ICM can cause intermittent or complete starting failure.
Other Potential Issues:
* Security System: If equipped with a factory or aftermarket security system, it might be preventing the engine from starting. Check for any warning lights or unusual behavior.
* Battery/Electrical: While it's cranking, a weak battery might not provide enough power for the ignition system to function properly. Test the battery voltage. Loose or corroded battery terminals can also cause problems.
* Mass Airflow Sensor (MAF): A faulty MAF sensor can cause the engine to run lean or rich, making it difficult or impossible to start.
* Engine Control Module (ECM): The computer that controls the entire engine. A faulty ECM is less likely but possible. This usually requires professional diagnosis.
Troubleshooting Steps:
1. Check the obvious: Fuel level, battery terminals, and spark plug wires visually.
2. Listen carefully: While cranking, listen for unusual sounds from the fuel pump (a whine).
3. Check for codes: Use an OBD-II scanner to check for diagnostic trouble codes (DTCs) stored in the ECM. This can pinpoint the problem area.
4. Test fuel pressure: Use a fuel pressure gauge to check fuel pressure at the fuel rail.
5. Test for spark: Remove a spark plug, ground it, and crank the engine to see if there's a spark.
If you're not comfortable working on your vehicle, take it to a qualified mechanic for diagnosis and repair. Attempting to troubleshoot these issues without experience can be dangerous. Remember safety first!
