1. Fuel System Issues:
* No Fuel: Empty tank, fuel pump failure (no pressure at the rail), clogged fuel filter, faulty fuel injectors, problems with the fuel pressure regulator. Check the fuel pressure at the rail.
* Bad Fuel: Old, contaminated, or incorrect fuel (wrong octane) can prevent starting.
* Fuel Delivery Problems: Leaks in the lines, restricted fuel lines, problems with the carburetor (if equipped) like a clogged float bowl or a stuck float.
2. Ignition System Problems:
* No Spark: Faulty ignition coil, bad ignition module (computer controlled ignition), corroded or loose wires, bad distributor cap or rotor (points-type ignition), faulty crankshaft position sensor (for electronic ignition), problems with the ignition switch.
* Weak Spark: Worn spark plugs, failing ignition coil, dirty distributor cap/rotor, low battery voltage.
* Timing Issues: Distributor timing is significantly off (though usually it'll crank, just not fire).
3. Compression Issues:
* Low Compression: Worn piston rings, worn valves, blown head gasket, cracked cylinder head or block. A compression test is necessary to diagnose this.
4. Starting System Problems:
* Dead or Weak Battery: Not enough cranking power to turn the engine over. Check the battery voltage.
* Bad Starter: The starter motor itself might be faulty (solenoid, motor windings). Listen closely for the starter's engagement – a click might indicate a bad solenoid.
* Bad Battery Cables: Corrosion or loose connections can prevent sufficient current flow.
* Faulty Neutral Safety Switch: Prevents starting unless the transmission is in Park or Neutral.
5. Other Potential Issues:
* Security System: An aftermarket alarm or immobilizer may be preventing the engine from starting.
* Engine Binding: A seized engine (due to lack of lubrication or other mechanical failure) will not turn over.
* Flooded Engine: Too much fuel in the cylinders can prevent starting. Try cranking for a few seconds, then pause for a minute, repeat several times.
* Incorrect Engine Settings: Incorrect carburetor adjustments or computer settings (on fuel-injected engines).
Troubleshooting Steps:
1. Check the obvious: Battery voltage, fuel level, and basic wiring connections.
2. Listen closely: Does the starter crank the engine? If so, how strongly? Do you hear any unusual noises?
3. Check for spark: Use a spark tester or a grounded spark plug wire to see if spark is present.
4. Check fuel pressure: Use a fuel pressure gauge to measure fuel pressure at the fuel rail.
5. Perform a compression test: If you suspect low compression, this is crucial.
Addressing a no-start issue requires a systematic approach. Start with the simplest checks (battery, fuel) and move towards more complex diagnostics (compression test, ignition system checks). If you're not comfortable working on your engine, it's best to take it to a qualified mechanic.
