* Spark: The most common reason for a car to crank but not start is a lack of spark. This could be due to:
* Ignition Coil: A faulty ignition coil won't deliver the high voltage needed to ignite the fuel-air mixture.
* Spark Plugs/Wires: Worn, fouled, or damaged spark plugs or wires can prevent spark from reaching the cylinders.
* Ignition Control Module (ICM): This module controls the ignition system; a malfunctioning ICM can interrupt the spark.
* Distributor (if equipped): Older vehicles might have a distributor; issues within it (rotor, cap, etc.) can disrupt spark delivery. The '93 Lumina might or might not have a distributor depending on the engine.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position; a faulty sensor prevents proper spark timing.
* Fuel Delivery (despite pump running): While you say the fuel pump is running, there could still be fuel delivery issues:
* Fuel Injectors: Clogged or faulty fuel injectors might not be spraying fuel properly into the cylinders, even if the pump is working.
* Fuel Pressure Regulator: This regulator maintains correct fuel pressure; a malfunction could lead to insufficient pressure at the injectors.
* Fuel Filter: A clogged fuel filter could restrict fuel flow, despite the pump working. While less likely given the pump runs, it's still possible.
* Air Intake: Make sure there are no obstructions in the air intake system.
Troubleshooting Steps:
1. Check for Spark: The easiest way is to use a spark tester on the spark plug wires. If no spark, focus on the ignition coil, ICM, distributor (if applicable), and CKP sensor.
2. Check Fuel Pressure: Use a fuel pressure gauge to measure the pressure at the fuel rail. This verifies the fuel pressure regulator and injector function. A low or no pressure reading indicates problems in those areas.
3. Inspect Spark Plugs: Remove and inspect the spark plugs. Look for fouling, damage, or excessive wear.
4. Inspect Air Intake: Ensure the air filter is clean and there are no blockages in the intake system.
5. Check for Codes: Use a OBD-I scanner (since it's a '93) to retrieve any diagnostic trouble codes (DTCs). These codes can provide clues about the problem.
It's important to systematically investigate these areas. If you're not comfortable working on your car's electrical and fuel systems, it's best to take it to a qualified mechanic for diagnosis and repair.
