1. Verify the Ignition Module Replacement:
* Correct Part: Double-check you installed the *correct* ignition module for your specific 1991 Cavalier 3.1L engine. There can be slight variations.
* Proper Installation: Ensure it's securely seated and all connections are clean and tight. A loose connection or incorrect installation is a common reason for problems even with a new part. Check the wiring harness for any damage near the module.
2. Fuel System:
* Fuel Pump: Listen carefully near the fuel tank for the whirring sound of the fuel pump when you turn the ignition key to the "on" position (don't crank the engine yet). If you don't hear it, the pump may be faulty or the fuel pump relay is bad.
* Fuel Pressure: This requires a fuel pressure gauge to measure the pressure at the fuel rail. Low or no pressure indicates a problem with the pump, filter, or pressure regulator.
* Fuel Filter: A clogged fuel filter can restrict fuel flow. Replace it as preventative maintenance.
3. Crankshaft Position Sensor (CKP Sensor):
* This sensor is crucial for the engine's timing. A faulty CKP sensor will prevent the engine from starting. It's often located on the engine block near the crankshaft. Inspect it for damage and consider testing its output with a multimeter (you'll need a wiring diagram to know which wires to test).
4. Distributor (If Equipped):
* Rotor and Cap: Inspect the distributor cap and rotor for cracks, carbon tracking, or wear. Replace if necessary. Even a small amount of moisture can cause starting issues.
* Distributor Shaft: Ensure the distributor shaft isn't worn or damaged.
5. Ignition Coil:
* While less likely after replacing the ignition module, a faulty ignition coil can also prevent starting. It's possible the module's failure damaged the coil. Test the coil's resistance with a multimeter (consult a wiring diagram for specifications).
6. Battery and Cables:
* Battery Voltage: Make sure the battery has sufficient charge. A weak battery can prevent the starter from cranking the engine. Test the battery voltage with a multimeter.
* Clean Connections: Clean the battery terminals and cable ends with a wire brush to ensure good electrical contact.
7. Starter Motor:
* Cranking: Does the engine crank over (turn over)? If not, you might have a problem with the starter motor, its solenoid, or related wiring.
8. Security System:
* Some Cavaliers have aftermarket or factory security systems that can prevent starting if a code isn't entered correctly or if the system is malfunctioning.
Troubleshooting Steps:
1. Start with the easiest checks: Battery, connections, and fuel pump sound.
2. Visual inspection: Look for any obvious signs of damage to wires, connectors, or components.
3. Use a multimeter: To test voltage, resistance, and continuity in the electrical system.
4. Consult a wiring diagram: A wiring diagram for your specific year and model Cavalier is essential for accurate testing. You can often find these online through repair manuals or forums.
5. Professional Assistance: If you're not comfortable with electrical testing or mechanical repairs, it's best to take your car to a qualified mechanic.
Remember safety first! Disconnect the negative battery cable before working on any electrical components. Good luck!
