How to troubleshoot ignition problems on a 1968 Ford Mustang GT Fastback (Bullitt)?

Ignition problems in a 1968 Ford Mustang GT Fastback (Bullitt) can manifest through symptoms such as difficulty starting the engine, engine misfires, or rough idling. These issues can be frustrating but are often resolvable through systematic troubleshooting. Below is a comprehensive guide on identifying and resolving ignition problems in this classic muscle car.

Step 1: Inspect the Ignition Coil

The ignition coil transforms the battery's low voltage to the high voltage needed to create a spark in the spark plugs. To locate the ignition coil, look for a cylindrical object about 6 inches long, often mounted on the engine block or firewall, with wires coming out of both ends.

1. First, visually inspect the coil for any cracks, burns, or damage.
2. Use a multimeter to measure the resistance. Check the vehicle’s manual for the correct resistance values. If they don’t match, the coil may need replacing.

Step 2: Check the Spark Plugs and Wires

Spark plugs ignite the fuel-air mixture in the engine's cylinders, and they are accessible by following the thick wires (spark plug wires) connected to each cylinder.

1. Remove each spark plug using a spark plug socket and inspect for wear and deposits. A healthy spark plug should appear light brown or grey with minimal deposits. Replace any plugs that appear fouled or worn.
2. Examine the spark plug wires for cracks or signs of wear. Replace any damaged wires to ensure good electrical conductivity.

Step 3: Inspect the Distributor Cap and Rotor

The distributor directs the high-voltage current from the ignition coil to the correct cylinder. The distributor cap and rotor are usually found at the front of the engine and consist of a cap with several terminals (one for each cylinder).

1. Remove the distributor cap by unscrewing the retaining screws. Examine it for cracks, carbon tracking, or corrosion on the terminals.
2. Check the rotor, which is located under the distributor cap, for signs of wear or damage. Replace both these parts if any issues are identified.

Step 4: Assess the Battery and Connections

A weak battery or poor connections can also cause ignition problems. The battery is typically located in the engine bay, to one side, and is a rectangular unit with two cables (positive and negative) connected to it.

1. Ensure the battery terminals are clean and free of corrosion. Use a wire brush to clean them if necessary.
2. Check the battery voltage with a multimeter; it should read around 12.6 volts when fully charged. If the voltage is low, charge the battery or consider a replacement.
3. Verify that all connections are tight and secure.

Step 5: Examine the Ignition Switch

The ignition switch, located on the steering column or dashboard, initiates the ignition process when turned. Problems with this switch can cause intermittent starting issues.

1. Insert the key and turn it to the "Start" position. Listen for clicks or whirring sounds indicating relay and starter motor operation.
2. If there's no sound, check the electrical connections to the ignition switch beneath the dashboard for signs of wear or damage. Reconnect or replace as necessary.

Step 6: Test the Starter Solenoid and Motor

The starter solenoid and motor are essential for starting the engine. The solenoid is a small cylinder often found on the firewall or near the battery, while the starter motor is mounted on the engine’s lower section.

1. Locate the starter motor and solenoid. Listen for a clicking noise when attempting to start the vehicle—this indicates a functioning solenoid.
2. If you hear no sound or the motor doesn’t engage, test the solenoid by bypassing it (connecting the terminals momentarily). If the starter motor engages, the solenoid is likely the problem.
3. Replace the starter solenoid or starter motor if needed.

By following these steps, you can systematically diagnose and address ignition issues in your 1968 Ford Mustang GT Fastback (Bullitt), ensuring it runs smoothly and reliably.