How to troubleshoot ignition problems on a 1967 Shelby GT500?

When dealing with ignition problems on a 1967 Shelby GT500, you might experience issues such as the car not starting, rough idling, or intermittent stalling. These problems can stem from various elements within the ignition system, such as the spark plugs, ignition coil, distributor, or ignition wiring. Here’s how to solve this issue:

Step 1: Check the Spark Plugs
First, locate the spark plugs, which can be identified by the thick wires running to each cylinder in the engine bay. Spark plugs are generally found at the top or side of the engine. They're small, cylindrical, and metal with ceramic insulators.

• Inspection: Remove one spark plug at a time using a spark plug socket and wrench. Inspect for wear and tear: burnt or fouled plugs, oil deposits, or excessive gap can indicate problems.
• Replacement: If any plug looks worn out, replace all spark plugs. Ensure you use correct gapping and torque specifications as per the Shelby GT500’s manual.

Step 2: Examine the Ignition Coil
Locate the ignition coil, typically mounted on the engine or the firewall. It looks like a cylindrical or rectangular box with wires running to and from it.

• Testing: Use a multimeter to check the primary and secondary resistance of the coil. Compare the readings to the manufacturer's specifications.
• Replacement: If the readings are off, replace the ignition coil. Make sure all connections are secure.

Step 3: Inspect the Distributor Cap and Rotor
The distributor cap is a plastic component that sits atop the distributor and connects to the spark plug wires. It’s usually round with multiple plug wire connections.

• Removal: Detach the plug wires from the distributor cap, making sure to note the correct order to avoid any mix-up during reinstallation.
• Inspection: Look for signs of carbon tracking, cracks, corrosion, or a worn-out rotor. Clean any debris and ensure all contacts are intact.
• Replacement: If there is damage, replace both the distributor cap and rotor.

Step 4: Inspect Ignition Wiring and Connections
Examine all ignition wires running from the distributor to the spark plugs and from the ignition coil. These are typically thicker wires, sometimes black or gray.

• Inspection: Look for fraying, burning, or any form of physical damage to the wires.
• Replacement: Replace any damaged wires with new, high-quality spark plug wires. Ensure all connections are tight and corrosion-free.

Step 5: Test the Ignition Switch
The ignition switch is located in the steering column and can influence the electrical flow to the ignition system.

• Access: To access it, you might need to remove parts of the steering column cover.
• Testing: Use a multimeter to ensure the switch is working properly when turned to the start position.
• Reinstallation: If defective, replace the ignition switch and ensure all connections are secure and functioning.

By following these steps, you should be able to diagnose and resolve most ignition issues on your 1967 Shelby GT500. Good luck!