1. Fuel System:
* Empty Tank: The most obvious! Check your fuel gauge and add fuel if necessary.
* Fuel Pump: Listen for the fuel pump whirring when you turn the key to the "on" position (before cranking). If you don't hear it, it might be faulty. You might need a helper to listen near the tank while you turn the key. If you have a fuel pressure gauge, that's the definitive test.
* Fuel Filter: A clogged fuel filter will restrict fuel flow. Inspect or replace it.
* Fuel Lines: Check for cracks, leaks, or kinks in the fuel lines.
* Fuel Injectors (or Carb): If it's fuel-injected, a faulty injector could be the problem (requires specialized tools to test). If it's a carburetor, it might be clogged or need adjustment (requires carburetor knowledge).
2. Ignition System:
* Spark Plugs: Check the spark plugs for wear, fouling (black or wet), or breakage. Replace them if needed. *Always disconnect the negative battery terminal before working on the ignition system.*
* Wires: Inspect the spark plug wires for cracks, damage, or loose connections.
* Distributor Cap and Rotor: Check for cracks, corrosion, or burnt contacts. Replace if necessary. (Applies to distributor-based ignition systems, less common in 1986 but still possible)
* Ignition Coil: A failing ignition coil won't produce enough spark. Testing requires a multimeter or a specialized ignition coil tester.
* Ignition Switch: A faulty ignition switch might not be sending power to the necessary components.
3. Air Intake:
* Air Filter: A severely clogged air filter restricts airflow to the engine. Replace it.
4. Battery and Electrical System:
* Battery Terminals: Corroded or loose battery terminals can prevent proper current flow. Clean them thoroughly.
* Battery Voltage: Test the battery voltage with a multimeter. It should be around 12.6V when fully charged. Low voltage can prevent starting.
* Starter Motor: While it's turning over, a weak starter motor might not have enough power to crank the engine fast enough. This requires more advanced testing.
5. Other Considerations:
* Sensor Issues: Modern fuel-injected systems rely on various sensors (like oxygen sensor, crankshaft position sensor, etc.). Faulty sensors can prevent starting.
* Timing Belt/Chain: A broken timing belt or chain will prevent the engine from running. (This is a major repair, and often requires engine disassembly)
Troubleshooting Steps:
1. Start with the easy checks: Fuel level, battery terminals, air filter.
2. Listen for the fuel pump.
3. Check the spark plugs.
4. Inspect the ignition system components.
5. If you're not comfortable working on your truck, take it to a mechanic.
Important Notes:
* Safety First: Always disconnect the negative battery terminal before working on the electrical system.
* Year and Model Specifics: The exact system and troubleshooting steps will vary depending on the exact make and model of your 1986 truck. A repair manual specific to your truck is invaluable.
* Professional Help: If you're not experienced with automotive repair, it's best to consult a qualified mechanic.
By systematically checking these areas, you should be able to narrow down the cause of your no-start issue. Remember to consult a repair manual or a qualified mechanic if needed.
