1. Verify the Obvious (But Important):
* Battery Terminals: Clean and tighten the battery terminals. Corrosion can dramatically increase resistance and prevent sufficient current flow.
* Battery Cables: Inspect the battery cables for any damage, fraying, or loose connections. A bad ground is a common culprit.
* Starter Motor: While unlikely if it's *almost* starting, a weak starter could cause this. Have someone try turning the key while you listen carefully near the starter for a weak click or grinding sound.
2. Crankshaft Position Sensor (CKP Sensor): This is a VERY common cause of no-start issues on these cars. A failing CKP sensor prevents the engine from receiving the signal it needs to fire.
* Check the sensor: This usually involves visually inspecting the sensor for damage or corrosion. It's often located on the engine block near the crankshaft pulley. Access may require removing some components. This is more advanced and requires some mechanical knowledge. It's best to consult a repair manual or a mechanic if unsure.
* Consider replacement: If the sensor looks suspect, replacing it is relatively inexpensive and often solves the problem.
3. Fuel Delivery:
* Fuel Pump: A weak fuel pump might provide enough fuel to almost start, then fail to maintain pressure. You might hear the pump prime briefly when you turn the key (listen near the fuel tank). If you don't hear it, this is a strong possibility.
* Fuel Filter: A clogged fuel filter can restrict fuel flow. It's a relatively inexpensive and easy component to replace.
* Fuel Pressure Regulator: A faulty fuel pressure regulator could be causing erratic fuel pressure. This is a more involved diagnostic process.
4. Ignition System:
* Ignition Coil(s): A weak or failing ignition coil could prevent proper spark delivery. This is more difficult to diagnose without specialized tools.
* Spark Plugs/Wires: While less likely to cause the *almost starting* symptom, inspect them for damage or wear.
5. Security System: If your Grand Prix has an aftermarket or factory alarm system, a malfunction could be preventing starting.
Troubleshooting Steps:
1. Start with the easiest: Clean battery terminals and check cables.
2. Listen carefully: Note any unusual sounds during cranking.
3. Check for codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the car's computer. This can often pinpoint the problem.
4. Visual inspection: Carefully inspect components related to the above suggestions. A repair manual is extremely helpful here.
5. Seek professional help: If you're not comfortable performing any of these checks or repairs yourself, take it to a mechanic specializing in GM vehicles. The CKP sensor is often the first thing a mechanic will test.
Remember safety first. Disconnect the negative battery terminal before working on any electrical components. If you're not comfortable working on cars, it's best to get professional help. The cost of a misdiagnosis can be higher than the cost of a mechanic.
