1. Ignition System: This is the most likely culprit.
* Spark: This is the crucial element. You need to verify if the engine is getting spark. A mechanic can easily check this with a spark tester. Common ignition system issues include:
* Ignition coil: A faulty coil won't deliver the necessary high voltage to the spark plugs.
* Ignition control module (ICM): This module controls the ignition coil. A bad ICM can prevent spark.
* Distributor cap and rotor (if applicable): Cracks or corrosion in these components can interrupt the spark delivery. (The Mark VIII might have a distributorless ignition system, but this is still worth checking if you have access.)
* Spark plugs and wires: Worn or fouled spark plugs or damaged wires can prevent proper spark.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position, crucial for timing the spark. A faulty CKP prevents the engine from firing.
2. Fuel System (Secondary Check): Though you hear the pump, there might still be fuel delivery issues.
* Fuel pressure: While the pump runs, it's crucial to verify *sufficient* fuel pressure. A low-pressure reading, even with the pump running, indicates a problem in the fuel lines, filter, or pressure regulator. A fuel pressure gauge is needed for this check.
* Fuel injectors: Even with sufficient pressure, clogged or faulty injectors can prevent fuel from reaching the cylinders. This requires more advanced diagnostics.
3. Computer System:
* PCM (Powertrain Control Module): The PCM controls many aspects of the engine. A malfunctioning PCM can cause a no-start condition. Diagnostic trouble codes (DTCs) should be retrieved using an OBD-I scanner (1993 vehicles don't use OBD-II).
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): This is the *first* step. You'll need an OBD-I scanner specific to a 1993 vehicle. The codes will point you in the right direction.
2. Verify Spark: This is the easiest and most important next step. If there's no spark, focus on the ignition system components listed above.
3. Check Fuel Pressure: If you have spark, check fuel pressure. Low pressure points to a fuel delivery problem.
4. Inspect Ignition Components: Visually inspect the coil, distributor cap, rotor (if applicable), spark plugs, and wires for damage or corrosion.
Important Note: Without the proper tools (spark tester, fuel pressure gauge, OBD-I scanner), accurate diagnosis will be difficult. If you're not comfortable working on cars, take it to a qualified mechanic. They have the tools and experience to quickly identify the problem.
