1. The Basics:
* Battery: Check the battery terminals for corrosion. Clean them with a wire brush and baking soda solution. Test the battery voltage with a voltmeter. It should read around 12.6 volts when not cranking. If it's low, charge the battery or replace it.
* Cables: Inspect the battery cables for damage, looseness, or corrosion. Make sure they're securely connected.
* Starter: Try turning the key to the "start" position. Do you hear *any* clicking sounds? A single click usually indicates a weak battery, a bad connection, or a failing starter solenoid. Multiple clicks might point to a low battery. No sound at all could mean a dead battery, bad cables, or a faulty starter motor or solenoid.
2. Ignition System:
* Ignition Switch: A faulty ignition switch prevents power from reaching the starter. This is less common but possible.
* Ignition Coil: This part generates the high voltage needed for the spark plugs. A faulty coil will prevent the engine from firing.
* Distributor (if equipped): Older S-10 Blazers might have a distributor. Check the rotor and cap for wear or damage. A faulty distributor could interrupt the spark to the cylinders.
* Spark Plugs & Wires: Worn or fouled spark plugs and damaged wires can prevent a spark. Check their condition and replace if necessary.
* Fuel Pump: If you hear nothing when you turn the key to the "start" position (besides the click of the solenoid maybe) and you don't smell any fuel, then you have a no-start condition that is NOT directly related to the starter. This should lead you to consider a faulty fuel pump relay, fuel pump itself, or perhaps a fuel filter blockage. The fuel pump should prime with a brief hum when you turn the key to the "on" position before cranking.
3. Other Possibilities:
* Security System (if equipped): An aftermarket or factory alarm system could be preventing the vehicle from starting.
* Neutral Safety Switch: This switch prevents the engine from starting unless the transmission is in park or neutral.
* Computer/Sensors: Problems with the PCM (Powertrain Control Module) or various sensors (crankshaft position sensor, camshaft position sensor, etc.) can cause a no-start condition. This requires more advanced diagnostic tools.
Troubleshooting Steps:
1. Start with the simplest checks: Battery, cables, and the starter motor and its related wiring.
2. Listen carefully: What sounds do you hear when you turn the key?
3. Visual Inspection: Look for anything obvious, like broken wires or loose connections.
4. If you have a multimeter: Use it to check battery voltage, and possibly test the voltage at the starter motor itself.
5. If basic checks fail: Consult a repair manual specific to your 1991 Chevy S-10 Blazer. These manuals provide detailed diagrams and troubleshooting guides.
6. Consider professional help: If you're not comfortable working on your vehicle, take it to a qualified mechanic.
Without more information on the specific symptoms (sounds you hear, smells, etc.), this is the best general advice. Provide more details and I can offer more targeted assistance.
