Fuel System:
* No fuel: This is the most common cause. Check the fuel pump (you might hear it hum when the key is turned to the "on" position before cranking – if not, it's a suspect). Inspect the fuel filter (it could be clogged). Look for any leaks in fuel lines. A faulty fuel pressure regulator could also be the culprit. A clogged fuel injector is another possibility.
* Low fuel: Sounds obvious, but make sure the tank isn't empty.
Ignition System:
* Spark plugs/wires: Worn, fouled, or loose spark plugs or wires can prevent ignition. Inspect for damage or corrosion.
* Distributor cap and rotor (if applicable): Cracks or corrosion in the distributor cap and rotor can interrupt the spark. Inspect for wear. (Note: the Astro's year might vary on this component - some had coil-on-plug ignition)
* Ignition coil (or coil packs): A faulty ignition coil (or individual coil packs) will prevent spark to the plugs. Testing is usually required to diagnose this.
* Crankshaft position sensor (CKP sensor): This sensor tells the engine's computer the position of the crankshaft. A faulty CKP sensor will prevent the engine from receiving the signal to fire.
* Cam sensor (CMP sensor): Similar to the CKP, a faulty CMP prevents proper ignition timing.
Other Potential Causes:
* Security system: An immobilizer or aftermarket alarm system might be preventing the engine from starting. Check if the key is recognized properly by the system.
* Battery: Although it's cranking, a weak battery might not provide enough power to start the engine. Test the battery voltage.
* Starter: While it's cranking, a failing starter might still not have enough power to spin the engine fast enough to start.
* Alternator: An alternator problem won't directly cause a no-start, but a fully discharged battery can certainly be a factor.
* PCM (Powertrain Control Module): A faulty PCM can prevent the engine from starting. This is usually a more difficult diagnosis.
* Air intake system: Check for obstructions in the air intake system that could prevent sufficient airflow.
Troubleshooting Steps:
1. Check the obvious: Fuel level, obvious leaks, and listen for the fuel pump.
2. Test the spark: Use a spark tester or even just hold a grounded spark plug wire near the engine block to see if you get a spark when cranking.
3. Check battery voltage: Make sure it's above 12V.
4. Get a code scan: A scan tool will pull trouble codes stored by the PCM, which can help point to the problem. Auto parts stores often offer this service for free.
If you're not comfortable working on your vehicle yourself, it's best to take it to a mechanic for diagnosis and repair. Trying to troubleshoot this without some basic mechanical knowledge can be frustrating and potentially damaging.
