Battery/Charging System:
* Dead Battery: This is the most common cause. A battery can fail suddenly due to age, corrosion on the terminals, a parasitic drain (something drawing power even when the car is off), or extreme cold. Check the battery voltage with a voltmeter. It should be around 12.6V when fully charged.
* Alternator Failure: If the alternator isn't charging the battery, it will eventually die, leading to a no-start condition. Testing the alternator's output voltage while the engine is running is necessary.
* Loose or Corroded Battery Cables: Check the connections at both battery terminals and the engine block for corrosion and tightness. Clean them with a wire brush if necessary.
Starting System:
* Starter Motor Failure: The starter motor itself could have failed. This is a common failure point in older vehicles. You might hear a clicking sound when you turn the key, which is a classic symptom of a failing starter.
* Starter Solenoid Failure: The solenoid is an electromagnet that engages the starter motor. A faulty solenoid will prevent the starter from turning. Again, you might hear clicking.
* Ignition Switch Problem: The ignition switch could be malfunctioning, preventing power from reaching the starter.
Fuel System:
* Fuel Pump Failure: The fuel pump might have stopped working. You might hear a humming sound from the fuel pump when you turn the key to the "on" position (but not while cranking). If not, the pump might be dead.
* Clogged Fuel Filter: A severely clogged fuel filter could restrict fuel flow to the engine.
* Empty Fuel Tank: This might seem obvious, but make sure you actually have fuel!
Other Potential Issues:
* Security System Issues: If the vehicle has an aftermarket or factory alarm system, a malfunction could prevent starting.
* Neutral Safety Switch: This switch prevents starting unless the transmission is in Park or Neutral. A faulty switch could be the culprit.
* Fuses and Relays: Check the fuses and relays related to the starting system and fuel pump.
* Crankshaft Position Sensor (CKP) or Camshaft Position Sensor (CMP): These sensors are crucial for the engine's timing. A faulty sensor will prevent the engine from starting. Often throws a diagnostic trouble code (DTC).
* Distributor Issues (if equipped): Older vehicles with distributors can experience problems like worn points or rotor issues.
Troubleshooting Steps:
1. Check the battery voltage.
2. Check battery cables for corrosion and tightness.
3. Listen carefully for any clicking sounds when turning the key.
4. Check the fuel level.
5. Have the alternator tested.
6. Check all fuses and relays related to starting and fuel.
7. If you hear clicking, suspect the starter, solenoid, or ignition switch.
8. If you hear nothing, suspect the battery, fuel pump, or other electrical components.
If you're not comfortable working on your car yourself, take it to a qualified mechanic for diagnosis and repair. They have the tools and expertise to pinpoint the problem more quickly and safely. Mentioning the sudden nature of the failure will help them in their diagnosis.
