1. Fuel System:
* Fuel Pump: Listen carefully near the fuel tank while someone cranks the engine. You should hear a whirring sound for a second or two when the key is first turned to the "on" position. If you don't hear it, the fuel pump may be bad or its relay is faulty.
* Fuel Filter: A clogged fuel filter restricts fuel flow. It's relatively inexpensive and easy to replace.
* Fuel Pressure: This requires a fuel pressure gauge to measure the pressure at the fuel rail. A low reading indicates a problem in the fuel pump, filter, or pressure regulator.
* Fuel Injectors: While less common as the initial problem, clogged or faulty injectors prevent fuel from reaching the combustion chamber. Testing injectors usually requires specialized tools.
2. Ignition System:
* Spark Plugs and Wires: Check the spark plugs for fouling (wet, oily, or excessively worn). Inspect the spark plug wires for cracks, damage, or loose connections. A simple spark test (using a spark plug tester or by carefully grounding a spark plug wire while cranking) can confirm spark.
* Distributor Cap and Rotor: Inspect the distributor cap and rotor for cracks, carbon tracking, or corrosion. These components distribute the high voltage to the spark plugs.
* Ignition Coil: A faulty coil won't produce sufficient high voltage for a spark.
* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the engine's rotational position. A faulty CKP sensor will prevent spark.
* Ignition Control Module (ICM): This module controls the ignition system's timing and spark. A faulty ICM can be a significant culprit.
3. Compression:
* Low Compression: This is less likely if it cranks normally but won't start. Low compression means the engine isn't creating sufficient pressure to ignite the fuel-air mixture. Requires a compression test to diagnose. Could indicate worn piston rings, blown head gasket, or valve problems.
Troubleshooting Steps:
1. Check for Spark: This is the quickest and easiest test.
2. Listen for the Fuel Pump: See above.
3. Check Fuel Filter: Easy to access and replace.
4. Inspect Spark Plugs and Wires: Simple visual inspection and easy replacement.
5. If you have a multimeter, you can test the fuel pump relay and other electrical components.
Important Considerations:
* Year and Model Specific Issues: The 1992 Jeep Cherokee had some known issues (e.g., specific to the Renix fuel injection system). Researching year-specific forums might reveal common problems.
* Security System: If it has an aftermarket or factory alarm/immobilizer, ensure it isn't preventing the engine from starting.
* Battery and Alternator: Although it cranks, a weak battery or failing alternator can still prevent starting. Test the battery voltage.
If you're not comfortable performing these checks yourself, take it to a mechanic. Providing more information on symptoms (e.g., any unusual noises, smells, or smoke) will help pinpoint the problem more accurately.
