1. Safety First:
* Disconnect the negative battery cable before starting any electrical work.
2. Check the Obvious:
* Battery Voltage: Test the battery voltage with a voltmeter. It should be around 12.6 volts when fully charged. A low voltage will prevent the ignition system from functioning correctly. Charge or replace the battery if necessary.
* Battery Cables and Connections: Inspect the battery cables and terminals for corrosion, looseness, or damage. Clean and tighten them if needed.
* Fuses and Relays: Check all fuses and relays related to the ignition system, specifically the ignition fuse (often labeled "IGN") and any relays controlling the ignition components (e.g., coil relay). Replace any blown fuses. A multimeter is helpful here to check relay operation.
* Ignition Switch: Ensure the ignition switch is functioning correctly. Try turning the key to different positions to see if there's any click or indication of power. If the switch is faulty, it will need to be replaced.
3. Focus on the Ignition System:
* Ignition Coil: This is a common culprit. A bad coil won't produce the high voltage needed for a spark.
* Visual Inspection: Check the coil for any visible damage, cracks, or corrosion.
* Testing: You can test the coil's primary and secondary resistance using a multimeter. Consult a wiring diagram or a repair manual for the specific resistance values for your 305. A simple test involves using a spark tester on the coil wire to check for spark directly. If there's no spark at the coil, the coil is bad or there is no power getting to the coil.
* Ignition Module (Electronic Ignition Control Unit - ECU): In many 305 applications, this component controls the ignition coil. If you have an electronic ignition system, a faulty ignition module will prevent spark. This often needs to be tested with a multimeter or a specialized diagnostic tool.
* Distributor (If applicable): If your 305 has a distributor (some HEI systems don't):
* Rotor and Cap: Inspect the rotor and distributor cap for cracks, carbon tracking, or corrosion. Replace if necessary.
* Pick-up Coil (inside distributor): This component generates the signal for the ignition module. Testing usually requires a multimeter or specialized equipment.
* Distributor Shaft: Make sure the distributor shaft isn't worn or damaged, affecting its rotation.
* Ignition Wires (Spark Plug Wires): Check the spark plug wires for cracks, damage, or corrosion. Replace any faulty wires. A simple visual inspection often suffices here. You can also use a spark tester to check for spark at each wire individually if you have a known good coil.
* Spark Plugs: Worn, fouled, or damaged spark plugs can prevent a spark. Inspect and replace if necessary. Gap the new plugs to the factory specification.
4. Crankshaft Position Sensor (CKP Sensor) (for some electronic ignition systems): This sensor tells the ECU the position of the crankshaft. A faulty CKP sensor will prevent the ECU from sending the signal to fire the coil. This requires testing with a multimeter.
5. Wiring: Check all the wiring related to the ignition system for any loose connections, breaks, or shorts. A wiring diagram is essential here to trace the circuit.
Systematic Troubleshooting:
The best approach is to start with the simplest checks (battery, cables, fuses) and then move progressively to the more complex components (coil, module, distributor). Use a wiring diagram to help you understand the electrical flow of the ignition system. A multimeter is invaluable for testing the different components and wiring.
When to Seek Professional Help:
If you're not comfortable working with automotive electrical systems, or if you've checked all the obvious components and still can't find the problem, it's best to take your vehicle to a qualified mechanic.
Remember to always consult a repair manual specific to your year and model of 305 Chevy engine for detailed wiring diagrams and component specifications. These manuals are readily available online and in auto parts stores.
