Ford Thunderbird/Cougar 1983-1997 Repair Guide

Diagnosis and Testing



Always turn the key OFF and isolate both ends of a circuit whenever testing for short or continuity.
Always disconnect solenoids and switches from the harness before measuring for continuity, resistance or energizing by way of a 12 volts source.
When disconnecting connectors, inspect for damaged or pushed-out pins, corrosion, loose wires, etc. Service if required.


Visually inspect the engine compartment to ensure that all vacuum lines and spark plug wires are properly routed and securely connected.
Examine all wiring harnesses and connectors for insulation damage, burned, overheated, loose or broken conditions.
Be certain that the battery is fully charged and all accessories OFF during the diagnosis.
The tools needed during this diagnosis procedure will be a suitable spark tester, 12 volt test lamp, small straight pins and Volt/ohm meter.

A spark plug with a broken side electrode is not sufficient to check for spark and may lead to incorrect results. All wire colors referred to in this part relate to the colors of the ignition module wires. When working with a wiring harness, the wire must be traced back to the ignition module for proper color identification. When instructed to inspect a wiring harness, both visual inspection and a continuity test should be performed. When making measurements on a wiring harness or connector, it is good practice to wiggle the wires while measuring.


  1. Disconnect the secondary (high voltage) coil wire from the distributor cap and install a spark tester between the coil wire and ground.
  3. Crank the engine. A good, strong spark should be noted at the spark tester. If spark is noted, but the engine will not start, check the spark plugs, spark plug wiring, and fuel system. If there is no spark at the tester:
    1. Check the ignition coil secondary wire resistance; it should be no more than 5,000 ohms per inch (25mm).
    3. Inspect the ignition coil for damage and/or carbon tracking.
    5. With the distributor cap removed, verify that the distributor shaft turns with the engine; if it does not, repair the engine as required.