1. Ignition System:
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position, crucial for precise spark timing. A faulty CKP will prevent spark and fuel delivery. It's relatively easy to access and test (usually with a multimeter).
* Camshaft Position Sensor (CMP): Similar to the CKP, but monitors the camshaft. A faulty CMP can also prevent spark and fuel.
* Ignition Coil(s): These deliver high voltage to the spark plugs. A faulty coil will result in no spark for the cylinder(s) it serves. Testing involves checking for continuity and resistance with a multimeter. Visually inspect for cracks or damage.
* Spark Plugs and Wires: Check for damage, corrosion, or wear on the spark plugs and their wires. Replace if necessary. A gap too large or too small can also affect spark.
* Ignition Control Module (ICM): This module controls the ignition coils. A faulty ICM can lead to no spark across multiple cylinders or even a complete no-spark condition.
* Distributor (if equipped): Some 2004 Optimas might still have a distributor. A faulty distributor cap, rotor, or internal components could cause the problem.
2. Fuel System:
* Fuel Pump: A faulty fuel pump won't deliver fuel to the engine. You can check the fuel pressure (requires a fuel pressure gauge) or listen for the pump's whirring sound when you turn the ignition key to the "on" position (before cranking).
* Fuel Pump Relay: This relay switches the power to the fuel pump. A faulty relay can prevent the pump from working. These are relatively inexpensive and easy to replace.
* Fuel Filter: A clogged fuel filter can restrict fuel flow. Replacing it is a relatively inexpensive preventative measure.
* Fuel Injectors: While less likely to cause a complete no-fuel situation, clogged or faulty injectors can prevent fuel delivery to the cylinders. Testing requires specialized tools.
* Cranking Sensor: This sensor senses when the engine is cranking, which triggers fuel delivery. A fault could prevent fuel from being supplied.
3. Computer/Electrical:
* PCM (Powertrain Control Module): The car's computer. A major fault here can shut down fuel and ignition. This is usually a last resort diagnosis, as it often requires professional tools and knowledge.
* Wiring Harnesses: Inspect for any damaged, broken, or corroded wiring, especially around the sensors and components mentioned above. A rodent could have chewed through wires.
Troubleshooting Steps:
1. Check for basic power: Make sure the battery is charged and connections are clean and tight.
2. Listen for the fuel pump: Turn the ignition key to "on" (don't crank) and listen for a whirring sound from the fuel pump (usually located near the fuel tank).
3. Visual inspection: Examine spark plugs, wires, and the ignition coil(s) for any obvious damage.
4. Check fuses and relays: Make sure all relevant fuses and relays are not blown.
5. Use a multimeter: Test the CKP, CMP, and ignition coils for continuity and resistance. Refer to a wiring diagram for your specific model.
Important Note: Without a proper diagnostic tool (like an OBD-II scanner), pinpointing the exact cause can be challenging. While the above steps offer a good starting point, a mechanic with the right tools can quickly identify the problem. A code reader can give you clues. Trying to diagnose this blindly can lead to replacing parts unnecessarily and wasting money.
