1. Visual Inspection:
* Distributor: Look for a distributor cap on the top of the engine, usually near the center. This cap has wires leading to the spark plugs. A distributor is the hallmark of a traditional ignition system. If you see one, you have a distributor-based ignition.
* Ignition Coil: Locate a roughly cylindrical component, often black and fairly substantial, that's connected to the distributor (usually with a single wire). This is the ignition coil.
* Ignition Module (or Control Module): This is less visually obvious. It's a smaller, usually rectangular box that may be mounted on the firewall, inner fender, or near the distributor. It's a critical part of the ignition system, controlling the coil's firing. Look for a module with wires leading to the distributor and the coil. The exact location varies slightly depending on the specific truck's configuration.
* Wiring: Trace the wires from the distributor to the coil and the ignition module (if found). This will help visualize the flow of the ignition system.
2. If you're unsure after the visual inspection:
* Consult a wiring diagram: A wiring diagram specific to your year, make, and model will show you exactly where all the components are and how they connect. You can find these online (search for "1989 Ford F150 302 wiring diagram") or in a repair manual.
* Listen for the sound of the coil firing: With the key turned to "ON," you may be able to hear a faint clicking sound near the ignition coil if the system is functioning correctly. However, don't rely solely on this.
What you'll likely find:
Given the year of your truck, it almost certainly has a distributor-based ignition system. This is the standard for that era. A newer electronic system wouldn't be common in a vehicle that old. The system will rely on the distributor to provide the timing for the spark, and the ignition module to electronically control the ignition coil.
Important Note: Working on ignition systems involves high voltage. Always disconnect the negative battery terminal before performing any work on the ignition system to prevent injury.
