1. Check the Ignition Module (or Ignition Control Module - ICM): The ICM is a crucial component that controls the coil pack. A faulty ICM will prevent the coil pack from firing. This is a common culprit in older Ford Explorers. It's usually located near the distributor (if equipped) or sometimes mounted on the firewall. You'll likely need a multimeter to test its voltage and resistance according to the specifications in your repair manual.
2. Inspect the Crankshaft Position Sensor (CKP Sensor): The CKP sensor tells the computer the engine's rotational position. Without a proper signal, the computer won't tell the coil pack to fire. Inspect the sensor for damage (broken wires, corrosion) and check its connection. A multimeter can be used to test its output signal.
3. Examine the Camshaft Position Sensor (CMP Sensor): Similar to the CKP sensor, the CMP sensor (if your engine has one) provides the engine's camshaft position. A faulty CMP sensor will also prevent sparking. Inspect it for damage and test its output signal.
4. Check the Distributor (if equipped): Some 1997 Explorers have distributors; others are distributorless. If yours has one, inspect the rotor and cap for cracks, wear, or corrosion. Ensure the rotor spins freely and makes good contact with the cap. Also, check the distributor's connection to the ignition module.
5. Inspect the Ignition Wiring: Carefully examine all the wiring from the ignition switch, through the ICM (if applicable), to the coil pack. Look for broken wires, frayed insulation, corrosion, or loose connections. Pay close attention to the connectors. A simple visual inspection is often enough to spot a damaged wire.
6. Test the Power Supply to the Coil Pack: Use a multimeter to verify that the coil pack is receiving the correct voltage and ground. The wiring diagram in your repair manual will show the correct testing points.
7. Check the PCM (Powertrain Control Module): The PCM is the "brain" of the engine. While less likely, a faulty PCM can prevent sparking. Diagnosing a PCM problem usually requires specialized tools and knowledge.
Important Considerations:
* Repair Manual: A repair manual specific to your 1997 Ford Explorer is invaluable. It will contain wiring diagrams, component specifications, and diagnostic procedures.
* Multimeter: A multimeter is essential for testing sensors and electrical components.
* Safety: Disconnect the negative battery terminal before working on the ignition system.
If you're not comfortable performing these tests yourself, it's best to take your Explorer to a qualified mechanic. Improperly diagnosing and repairing ignition problems can lead to further damage.
