* Ignition Switch: This is the most common culprit. The switch might be worn, dirty, or failing internally. Holding the key bridges the connection that's failing intermittently. This is a high-probability suspect given the symptoms.
* Starter Solenoid: This is an electromagnetic switch that engages the starter motor. A faulty solenoid might not be making a consistent connection, requiring the constant pressure from the key to maintain it.
* Starter Motor: While less likely than the ignition switch or solenoid, a worn or failing starter motor could also exhibit this symptom. The brushes inside might be worn, leading to intermittent contact.
* Wiring: Corroded, loose, or damaged wiring in the starting circuit can interrupt the connection. Check all the wiring between the ignition switch, solenoid, and starter motor.
* Neutral Safety Switch (Automatic Transmission): This switch prevents the engine from starting unless the transmission is in Park or Neutral. A faulty switch could be preventing the starter from engaging unless the key is held in the start position, possibly forcing a connection.
Troubleshooting Steps:
1. Check the battery and cables: Make sure the battery is charged and the terminals are clean and tight. A low battery can exacerbate starting problems.
2. Inspect the ignition switch: This might require some disassembly. If you're not comfortable with car repair, take it to a mechanic. Look for any signs of damage, corrosion, or looseness.
3. Test the starter solenoid: This can involve using a jumper wire to bypass the solenoid (but be extremely careful!). If the starter cranks when bypassed, the solenoid is the likely problem. This should only be attempted if you are knowledgeable about automotive electrical systems.
4. Listen carefully while attempting to start: If you hear a clicking sound, it's often an indication of a failing starter solenoid or low battery. A grinding noise points to a starter motor problem.
5. Check the Neutral Safety Switch (if automatic): Make sure the transmission is firmly in Park or Neutral. If you suspect this switch, testing it will require a multimeter and some electrical knowledge.
Recommendation:
Given the potential dangers of working with automotive electrical systems, it's best to take your 1994 Ford Explorer to a qualified mechanic for diagnosis and repair. Continuing to drive with a faulty ignition system could lead to further problems or even a dangerous situation. The cost of diagnosis and repair will likely be less than the potential cost of a more significant electrical failure or damage.
