1. Ignition System Components:
* Ignition Coil: This is a common point of failure. A visual inspection for cracks or obvious damage is a good start. You'll need a multimeter to check for primary and secondary resistance (consult a repair manual for specifications). A bad coil will show readings outside the acceptable range.
* Ignition Module (or Ignition Control Module - ICM): This component controls the coil's firing. Again, a visual inspection is first, then testing with a multimeter according to the repair manual's specifications. This often requires more advanced diagnostic skills.
* Distributor (if equipped): Older Aerostars might have a distributor. Check the rotor and cap for cracks, corrosion, or worn contacts. The pickup coil within the distributor can also fail. A visual inspection is critical, and a multimeter can be used to test the coil's resistance (consult a repair manual).
* Cranking Sensor (Crankshaft Position Sensor - CKPS): This sensor tells the computer when the engine is turning over. A faulty CKPS prevents the ignition system from firing. You'll need a multimeter to test its output while cranking the engine (consult a repair manual).
* Cam Position Sensor (CAM): Some models had a camshaft position sensor. A malfunctioning sensor prevents proper timing signals. Testing requires a multimeter and consultation of repair manuals for specific testing instructions.
* Ignition Switch: A failing ignition switch may not send power to the rest of the ignition system. Check that power is reaching the coil and other components when the key is turned to the "start" position.
2. Wiring and Connections:
* Loose or Corroded Wires: Inspect all wiring related to the ignition system, looking for broken, frayed, or corroded wires. Pay close attention to connections at the coil, distributor (if applicable), sensors, and ignition switch. Clean or repair any damaged wiring.
* Fuses and Relays: Check all fuses related to the ignition system. Also, there might be relays involved – check their operation.
3. Computer (PCM/ECM):
* PCM/ECM Failure: The Powertrain Control Module (PCM) or Engine Control Module (ECM) controls the ignition system. A faulty PCM/ECM is less likely but possible. Diagnosis usually requires a scan tool to read diagnostic trouble codes (DTCs).
Troubleshooting Steps:
1. Visual Inspection: Start with a thorough visual inspection of all ignition system components and wiring.
2. Check for Spark: Use an inline spark tester to check for spark at the spark plug wires. This is the most direct way to determine if the problem is pre-spark or post-spark.
3. Multimeter Testing: Use a multimeter to test the components mentioned above, referring to a repair manual for specific resistance and voltage readings.
4. Obtain a Repair Manual: A factory service manual is essential for this type of troubleshooting. It will provide wiring diagrams, component specifications, and diagnostic procedures. Haynes and Chilton manuals are also available but might not be as detailed.
5. Professional Help: If you're not comfortable working with automotive electrical systems, consider seeking help from a qualified mechanic.
Remember safety first! Disconnect the negative battery terminal before working on any electrical components. If you're unsure about any step, consult a professional. A misdiagnosis can lead to further damage or injury.
