1. The Basics (Check these first):
* Battery: Is the battery charged and the terminals clean and tight? A weak battery can prevent the ignition system from working properly. Test the voltage with a multimeter. Should be around 12.6V when not running.
* Ignition Switch: Is the ignition switch working correctly? Try turning the key all the way to the "start" position and listen for the starter motor engaging. If you have no cranking at all, the problem is before the ignition system. If it cranks but no spark, suspect ignition system issues.
* Fuses: Check any fuses related to the ignition system. The location varies depending on your truck's trim level, so consult your owner's manual.
2. The Ignition System (If the basics are OK):
* Coil: Test the coil's primary and secondary windings with a multimeter. A bad coil won't produce the high voltage needed for a spark. You can also visually inspect it for cracks or damage.
* Ignition Module (or Electronic Ignition Control Unit - ECU): Many '73 Chevy pickups used electronic ignition. The module is a small box; it controls the coil's firing. These can fail and are often difficult to test without a specific tool or oscilloscope. If you have a points and condenser system, skip this step and go to the next.
* Distributor:
* Points and Condenser (if applicable): If your truck has points and a condenser (older system), check for wear, corrosion, or damage. They need to be properly gapped.
* Rotor and Cap: Inspect the rotor and distributor cap for cracks, carbon tracking, or corrosion. A simple visual inspection is often enough to determine a faulty part.
* Distributor Shaft: Ensure the distributor isn't loose or damaged. A worn distributor shaft can cause erratic timing or no spark.
* Wires: Check all the ignition wires (from the coil to the distributor, distributor cap to spark plugs, etc.) for damage, fraying, or loose connections. Replace any suspect wires.
* Spark Plugs: Check the spark plugs' condition. They should be clean and properly gapped. Try swapping in a new set as a test. Fouled plugs can prevent a spark.
* Pick-up coil (in the distributor): This sends a signal to the ignition module (or points). A faulty pick up coil prevents the ignition from firing. Requires testing with a multimeter.
3. Testing for Spark:
The most reliable way to diagnose a no-spark issue is to use an inline spark tester. This connects in line with your spark plug wire and lets you see if a spark is present. If you don't have one, a basic test is to remove a plug wire, attach a plug to it, ground the plug to the engine block, and crank the engine. You should see a spark jump the gap.
4. Where to start:
The easiest and most cost-effective places to begin are:
1. Battery and Connections: A simple check, often overlooked.
2. Wires: Look for obvious damage. It's relatively cheap to replace them.
3. Spark Plugs: Easy to check and replace.
4. Distributor Cap and Rotor: Simple visual inspection.
5. Seeking Help:
If you are not comfortable working on your vehicle's electrical system, consider taking it to a qualified mechanic. Incorrectly diagnosing and fixing electrical issues can lead to further damage.
Remember to always disconnect the negative battery terminal before working on any part of the ignition system. Safety first!
