* Ignition System: Moisture can short out the ignition coil, distributor cap, rotor, or spark plug wires. This prevents the spark needed to ignite the fuel-air mixture. This is a very common cause.
* Distributor: If your Blazer has a distributor (rather than coil-on-plug ignition), water entering the distributor can cause serious issues.
* Wiring Harness: Age and exposure to the elements can cause the wiring harness to deteriorate. Rainwater can easily penetrate cracks and cause shorts. Look for areas where the harness runs close to the body and might retain water.
* Sensors: Various sensors (like the crankshaft position sensor, camshaft position sensor, or MAP sensor) are susceptible to moisture. A faulty sensor will prevent the engine from receiving the correct signals to start. These are often located in exposed areas.
* Computer/ECU: While less likely, water intrusion into the engine control unit (ECU) is possible, leading to complete system failure. This is a more serious problem requiring professional attention.
* Battery Terminals/Connections: Corrosion on the battery terminals can worsen with rain, leading to poor electrical contact and preventing the engine from cranking. Clean and tighten these connections.
* Alternator: While unlikely to *prevent* starting, a failing alternator might not charge the battery sufficiently after being depleted by repeated starting attempts in wet conditions.
Troubleshooting Steps:
1. Check the battery terminals: Clean them thoroughly with a wire brush and baking soda/water solution. Make sure the connections are tight.
2. Inspect the distributor (if applicable) and ignition system components: Look for any signs of corrosion, water damage, or loose connections. Replace any damaged parts.
3. Check for obvious signs of water intrusion: Look carefully under the hood and around electrical components for evidence of water.
4. Try drying out the affected areas: If you find wet components, try to carefully dry them with a hairdryer (on a low setting) or compressed air. Do not attempt this with the battery or while the engine is running.
5. Have a mechanic check the wiring harness: This can be a difficult problem to diagnose without professional tools.
If you're not comfortable working on your car's electrical system yourself, it's best to take it to a qualified mechanic. Ignoring the problem could lead to more serious (and expensive) damage.
