* Fuel System Issues:
* Empty or Low Fuel: The most obvious! Check your fuel gauge.
* Fuel Pump Failure: The pump might be failing to deliver fuel to the engine. You might hear a faint whine from the fuel pump when the key is turned to the "on" position (but not cranking). A mechanic can test the fuel pressure.
* Clogged Fuel Filter: A clogged filter restricts fuel flow.
* Fuel Injector Problems: One or more injectors might be clogged or faulty, preventing fuel from reaching the cylinders.
* Bad Fuel Pressure Regulator: This regulates fuel pressure in the system; a faulty one can cause inconsistent fuel delivery.
* Ignition System Problems:
* Spark Plug Issues: Worn, fouled, or damaged spark plugs prevent ignition. These are relatively easy to check and replace.
* Ignition Coil Problems: The coil provides the high voltage needed for sparking; a faulty coil will prevent one or more cylinders from firing.
* Distributor Issues (if applicable): Older vehicles might use a distributor. Issues within it can affect ignition timing and spark delivery. The Alero is likely to have coil-on-plug ignition.
* Ignition Control Module (ICM): This module controls the ignition system; a faulty ICM can prevent proper sparking.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the crankshaft's position. A faulty sensor prevents the computer from knowing when to send the spark.
* Cam Position Sensor (CMP): Similar to the CKP sensor but monitors the camshaft position; crucial for ignition timing.
* Other Potential Problems:
* Security System Issues: The car's anti-theft system might be preventing the engine from starting. Try checking your key fob's battery, or if there's a separate anti-theft system switch.
* Low Battery Voltage: A weak battery might crank the engine slowly, preventing it from starting. Have the battery and charging system tested.
* Starter Motor Issues (less likely): While you say it cranks, a failing starter might still be contributing to the problem by not spinning fast enough.
* Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. A dirty or faulty MAF can disrupt the air/fuel mixture and prevent the engine from starting.
* Engine Control Module (ECM): Rare, but a failing ECM can cause various starting problems. This is usually diagnosed by a mechanic using diagnostic tools.
Troubleshooting Steps:
1. Check the Obvious: Fuel level, battery voltage (have it tested), and easily accessible fuses.
2. Listen Carefully: Pay attention to any unusual sounds during cranking (e.g., clicking, whining).
3. Visual Inspection: Look for any obvious signs of damage to wires, connections, or components.
4. Check Spark: Use a spark tester to check if spark plugs are firing. (This can be dangerous, so take caution or consult a mechanic).
5. Get a Diagnostic Scan: Take the car to a mechanic or auto parts store that can perform a diagnostic scan. This can identify fault codes stored in the ECM, pointing to the likely cause.
Without more information or diagnostics, it's impossible to pinpoint the exact cause. Start with the simpler checks and proceed to more involved diagnostics if needed. A mechanic is your best bet for a definitive diagnosis and repair.
