1. Ignition System: The lack of spark is the most critical issue.
* Cranking Sensor (Crankshaft Position Sensor): This sensor tells the computer the engine is turning, triggering the spark. A faulty sensor prevents the computer from initiating the spark. Test it with a multimeter or replace it as it's a common failure point.
* Ignition Coil: This boosts the low voltage from the ignition system to create the high voltage needed for the spark plugs. A visual inspection for cracks or damage is a good starting point. Testing with a multimeter is more definitive.
* Ignition Control Module (ICM): This module controls the ignition coil's firing. Often located near the distributor (if your model has one), it can fail and prevent spark. Testing is usually done with a specialized tool or by comparison to a known good ICM.
* Distributor (if applicable): Some 1998 Wranglers might have a distributor. Check for proper cap and rotor condition, and ensure the rotor spins freely and makes good contact. Worn distributor components can prevent spark.
* Spark Plugs and Wires: Inspect for cracks, corrosion, or damage to the spark plugs and wires. Replace if necessary; it's a cheap and easy check.
* Wiring: Check for damaged, corroded, or loose wiring throughout the ignition system. Pay close attention to connections at the coil, distributor (if applicable), and crankshaft position sensor.
2. Fuel System: The lack of fuel needs investigation too.
* Fuel Pump: A non-functioning fuel pump prevents fuel from reaching the engine. You can listen for the fuel pump's prime sound (a whirring noise) when the ignition is turned on. If you don't hear it, it could be faulty or the relay/fuse is blown.
* Fuel Pump Relay: The relay is an electrical switch that activates the fuel pump. A bad relay will prevent the pump from running. Swap it with a known good relay to test.
* Fuel Filter: A clogged fuel filter restricts fuel flow to the engine. Replacing this is inexpensive and may resolve the problem.
* Fuel Injectors: While less likely to cause a complete lack of fuel (they'd usually give a sputtering start), a complete failure of all injectors is possible. This requires a more specialized test.
* Fuel Pressure Regulator: A faulty regulator could leak fuel pressure, preventing the engine from receiving enough fuel.
3. Computer/PCM (Powertrain Control Module): A failing PCM can prevent both spark and fuel delivery. This is a more involved diagnosis and often requires professional tools or a replacement PCM.
Troubleshooting Steps:
1. Check for power at the fuel pump and ignition coil. This helps isolate whether the problem lies in the power supply or the components themselves.
2. Listen for the fuel pump prime. If you don't hear it, check the fuel pump relay and fuse.
3. Check spark plugs and wires.
4. Test or replace the crankshaft position sensor. This is often the easiest and cheapest place to start.
5. Visually inspect the ignition coil and distributor (if applicable) for damage.
6. Use a multimeter to test the coil and other ignition components. This requires some electrical knowledge.
Important Note: If you're not comfortable working with automotive electrical systems, it's best to take your Jeep to a qualified mechanic. Improperly working with car electrical systems can be dangerous. The lack of both spark and fuel indicates a potentially serious problem that needs a proper diagnosis.
