* Fuel System Problems:
* Empty or low fuel: The most obvious, but always worth checking.
* Fuel pump failure: The pump may be weak or not working, preventing fuel from reaching the engine. You might hear a faint whine from the fuel pump when the key is turned to the "on" position (before cranking). Lack of whine suggests a problem.
* Clogged fuel filter: A blocked filter restricts fuel flow.
* Bad fuel injectors: These deliver fuel to the cylinders. A faulty injector or several could prevent proper combustion.
* Fuel pressure regulator: This maintains proper fuel pressure. A failing regulator can lead to low pressure.
* Ignition System Problems:
* Faulty ignition coil: This provides the spark to ignite the air/fuel mixture. A failing coil can cause misfires or no spark at all.
* Spark plugs: Worn, fouled, or damaged spark plugs prevent proper ignition.
* Ignition control module (ICM): This controls the ignition system. A faulty ICM can prevent the engine from firing.
* Distributor cap and rotor (if applicable): Cracks or corrosion can disrupt the spark delivery. (Less likely in a 2003, depending on engine.)
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A faulty CKP prevents proper timing of the spark.
* Cam Position Sensor (CMP): Similar to the CKP, but monitors camshaft position.
* Other Possibilities:
* Security System Issues: The vehicle's anti-theft system may be preventing the engine from starting.
* Low Battery Voltage: While it cranks, a weak battery might not provide enough power to the ignition system. Test the battery voltage.
* Starter Issues (less likely): Though it's cranking, a failing starter *could* be contributing to insufficient power for the ignition system.
* Poor Engine Compression: Worn piston rings or valve problems can lead to low compression, preventing the engine from firing even with spark and fuel. This requires a compression test.
Troubleshooting Steps:
1. Check the obvious: Fuel level, battery voltage.
2. Listen carefully: Do you hear the fuel pump prime when you turn the key on?
3. Check spark: A simple spark tester can check if spark is reaching the plugs.
4. Inspect visually: Look for any obvious signs of damage or corrosion in the ignition system.
5. Consult a repair manual: A factory service manual or a reputable online resource specific to your Suburban's engine (likely a Vortec) will provide detailed diagnostic procedures and wiring diagrams.
This is not an exhaustive list, but it covers many of the common causes. If you're not comfortable working on your vehicle yourself, taking it to a qualified mechanic is recommended. They have the tools and expertise to diagnose the problem accurately. Provide them with the details of what's happening to help speed the diagnosis.
