* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A faulty CKP sensor will prevent the computer from properly timing the fuel injection and ignition, even with spark and fuel present. This is a very common cause of no-start issues that aren't immediately obvious.
* Camshaft Position Sensor (CMP): Similar to the CKP sensor, a faulty CMP sensor affects timing. On some models, this is integrated with the CKP.
* Ignition Module (or coil pack if it's coil-on-plug): While you said it's getting fire, the spark might be weak or inconsistent. A failing ignition module or coil pack can cause this. Check the spark strength with a spark tester at each plug wire. Don't just assume a visible spark is strong enough.
* Wiring harness issues: A corroded, damaged, or loose wire in the ignition system, fuel system, or even the ground could be interrupting the signal. Carefully inspect the wiring harness, paying close attention to connectors and areas prone to wear. A wiring diagram specific to your year and model will be helpful here.
* Neutral Safety Switch: Prevents starting unless the transmission is in Park or Neutral. If this is faulty, the car won't crank, even if the key is turned. Check that it's working correctly.
* Alternator (less likely, but possible): A completely dead battery might start the car for a few seconds, but a failing alternator can't sustain a starting current. Check the alternator's output voltage while cranking.
* Immobilizer System (if equipped): Some 1998 Mustangs may have had an anti-theft system. A malfunctioning immobilizer can prevent starting. Check your key and ensure the immobilizer isn't the culprit.
* Fuel pressure regulator: Could be leaking pressure even with fuel in the system. A fuel pressure gauge test would be needed to verify.
Troubleshooting Steps:
1. Check the CKP and CMP sensors: These are relatively inexpensive and easy to replace. Start with these.
2. Thoroughly inspect the wiring harness: Look for any damage, corrosion, or loose connections.
3. Test the spark: Use a spark tester to verify the strength of the spark at each cylinder.
4. Check fuel pressure: Use a fuel pressure gauge to verify adequate fuel pressure at the rail.
5. Test the alternator: Measure the voltage output of the alternator while cranking the engine.
6. Verify Neutral Safety Switch operation.
7. Consult a wiring diagram: This is crucial for tracing wires and identifying components. You can often find these online for free, though a Haynes or Chilton manual may be helpful as well.
Remember safety first! Disconnect the negative battery terminal before working on any electrical components. If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic. They have the tools and experience to diagnose and repair these more complex issues.
