* Starter Motor Issues: Even though it's turning over, the starter motor might be weak or failing. It could be struggling to generate enough torque to fully crank the engine. This is less likely if it's turning over *strongly*.
* Ignition System Problems: This is a very common cause. Several components could be at fault:
* Ignition Coil: This delivers the high voltage spark to the spark plugs. A failing coil won't produce the necessary spark to ignite the fuel-air mixture.
* Spark Plugs/Wires: Worn, fouled, or damaged spark plugs or wires prevent a proper spark. Check for corrosion, cracks, or gaps that are too wide.
* Distributor (if equipped): Older vehicles often have a distributor that may have worn components or internal issues. This is less likely in a '95 Grand Prix, as many were moving away from distributors by then, but still a possibility.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position, essential for proper ignition timing. A faulty CKP prevents the engine from receiving the spark.
* Cam Position Sensor (CMP): Similar to the CKP, a faulty CMP sensor can prevent proper ignition timing.
* Fuel System Problems:
* Fuel Pump: A failing fuel pump won't deliver fuel to the engine, preventing combustion. You might hear the pump prime (a whirring sound) when you turn the key, but it could be weak or not working altogether.
* Fuel Filter: A clogged fuel filter restricts fuel flow, starving the engine.
* Fuel Injectors: Clogged or malfunctioning fuel injectors won't spray fuel into the cylinders.
* Security System: Some vehicles have anti-theft systems that might be preventing the engine from starting.
Troubleshooting Steps:
1. Check for Spark: The easiest way is with a spark tester on a spark plug wire. If you don't have one, you may be able to visually inspect the plug gap for a spark when cranking (but this is dangerous due to exposed high voltage).
2. Listen for the Fuel Pump: Turn the key to the "on" position (without cranking). You should hear a brief whirring sound from the fuel pump. If not, the pump may be faulty.
3. Check Fuel Pressure (Advanced): This requires a fuel pressure gauge and is best left to someone with experience.
4. Check for Error Codes: A code reader can read diagnostic trouble codes (DTCs) stored in the car's computer, providing clues to the problem.
5. Visual Inspection: Look for any obvious signs of damage to wiring, loose connections, or other problems.
Recommendation: If you're not comfortable working on cars, it's best to take it to a qualified mechanic. Diagnosing this problem requires systematic testing to pinpoint the faulty component. Trying to fix it blindly could lead to further damage.
