1. Simple Checks (Easiest First):
* Ignition Switch: Is the key fully turned to the "ON" or "START" position? A faulty ignition switch can prevent power from reaching the rest of the ignition system.
* Fuses/Relays: Check the fuses and relays related to the ignition system. Your owner's manual will show you the fuse box layout and what fuses control the ignition. A blown fuse is a simple fix.
* Battery and Connections: A weak or dead battery, or corroded battery terminals, will prevent sufficient power from reaching the ignition system. Clean the terminals and test the battery voltage.
* Ignition Coil: A faulty ignition coil won't produce the high voltage needed for a spark. This requires testing the coil's primary and secondary windings with an ohmmeter (following the specifications in your repair manual).
2. Distributor Specific Issues:
* Distributor Cap and Rotor: These are prone to wear and carbon buildup, leading to poor spark distribution or no spark at all. Inspect for cracks, burns, or excessive corrosion. Replacement is inexpensive.
* Worn or Damaged Distributor Points (if equipped): Older systems use points; if yours does, inspect for wear, pitting, or incorrect gap. These are less common in 1985, but possible depending on the specific engine. (Most likely this uses an electronic ignition system).
* Distributor Pickup Coil (Electronic Ignition): This is a critical component in electronic ignition systems. A faulty pickup coil won't generate the signal needed to trigger the ignition module. Testing this usually requires an oscilloscope or a specialized ignition system tester.
* Ignition Control Module (or Ignition Module): This module receives the signal from the pickup coil and controls the ignition coil. A faulty module will prevent spark. This will require testing, often with a multimeter or specialized testing equipment.
3. Other Potential Problems:
* Wiring: Check all wiring connected to the distributor, ignition coil, and ignition control module for breaks, shorts, or corrosion. A damaged wire can interrupt the electrical signal.
* Crankshaft Position Sensor (CKP Sensor): In some electronic ignition systems, the CKP sensor tells the ignition module when to fire. A faulty sensor can prevent spark.
* Computer/ECM Issues (Less Likely): In some instances, a problem with the Engine Control Module (ECM) can affect ignition timing and spark delivery. This is less likely to cause a complete lack of spark, but is a possibility if the other issues have been ruled out.
Troubleshooting Steps:
1. Start with the simple checks (battery, fuses, ignition switch).
2. Visually inspect the distributor cap and rotor for obvious damage.
3. Use a multimeter to test the ignition coil and other components according to the specifications in a repair manual for your specific vehicle. Attempting to test components without a service manual can lead to incorrect readings and damage.
4. If you're not comfortable with electrical testing, take it to a qualified mechanic. Improper testing can lead to more damage and expense.
Important Note: A repair manual specific to your 1985 Chrysler Fifth Avenue is invaluable for this type of troubleshooting. It will provide diagrams, component locations, testing procedures, and specifications. Without one, you risk damaging components or misdiagnosing the problem.
