Owner's Problem Description
The owner of a 1997 Pontiac Transport reports intermittent starting issues. The vehicle won't crank over despite having new battery and tested alternator. When the key is turned, only a click is heard, and lights come on. Sometimes, the engine starts but attempts to stall. The battery shows a bulge, indicating possible internal failure.
Professional Technical Analysis
This case involves a 1997 Pontiac Transport with a 3.4L V6 engine, approximately 150,000 miles. The vehicle intermittently fails to start, indicated by a clicking sound upon turning the key, with lights illuminating on the dashboard. The owner has replaced the battery twice and confirmed the alternator is functioning properly. However, the current condition of the battery shows a bulge, suggesting potential internal failure, which can lead to insufficient power delivery during cranking. The battery's inability to maintain voltage may cause the starter to engage poorly or not at all, leading to the 'no crank' condition. The electrical connections should be inspected for corrosion or loose terminals, particularly at the battery posts and starter solenoid. A significant voltage drop may occur under load, and a weak battery can result in the starter dragging or failing to engage entirely. Given the symptoms, it is critical to verify the integrity of the battery and its connections, as well as the functionality of the starter motor. The symptoms of the engine attempting to stall after starting indicate potential fuel delivery issues or issues with the ignition system, which may also need to be examined.
Possible Causes
Most common causes (ordered by frequency):
- Battery Internal Failure: The bulging battery indicates internal damage or cell failure, which can lead to insufficient cranking power. A healthy battery should hold a charge and show 12.6V at rest and maintain above 10.5V during cranking. A bulging battery should be replaced immediately to avoid further complications. Use OEM part number AC Delco 75-6 for replacement. - Visual inspection shows battery bulge, multimeter reading below 12V under load, and intermittent no-crank condition.
- Starter Motor Failure: The starter motor may be failing, especially if it only clicks without turning the engine over. Testing the starter solenoid and the motor itself for resistance (should be around 0.5 to 1.0 ohm) can confirm its condition. If the starter is faulty, replace it with OEM part number 10465236. - Clicking sound during start attempt without engine cranking, resistance test of starter shows values outside of range.
- Corroded or Loose Battery Connections: Poor connections can lead to inadequate power delivery to the starter. Ensure all connections at the battery terminals and starter solenoid are clean and tight. A typical resistance value should be less than 0.5 ohms for the connections to ensure efficient operation. - Visual inspection reveals corrosion at battery terminals, resistance tests show values above 0.5 ohms.
- Voltage Drop During Cranking: A significant drop in voltage (below 9V) during cranking indicates a potential issue with the battery or connections. A battery tester can be used to conduct a load test, which should maintain above 9.6V under load for a healthy battery. - Load test reveals drop below 9V during cranking, indicating battery failure.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Battery and Connection Inspection: Start with a thorough visual inspection of the battery for bulging or leaks. Check the battery terminals for corrosion and ensure tight connections. Use a multimeter to measure the battery voltage at rest and during cranking. Voltage should be at least 12.6V when resting and above 10.5V during cranking. If any issues are found, replace the battery and clean the connections.
- STEP 2 - Starter Motor Testing: If the battery is confirmed functional, proceed to test the starter motor. Check for proper operation by bypassing the solenoid with a screwdriver to see if the motor spins. Measure the resistance of the starter motor (should be 0.5-1.0 ohms). If it fails to engage, it may need replacement.
- STEP 3 - Voltage Drop Testing: Perform a voltage drop test on the battery cables and connections while attempting to crank the engine. This helps identify any excessive resistance in the circuit that could prevent the starter from receiving adequate power. Aim for less than 0.5V drop across each connection.
- STEP 4 - Final System Check: After addressing any issues found in previous steps, perform a final check by attempting to start the vehicle. Monitor the voltage during cranking and ensure all electrical systems function correctly. Ensure that the engine runs smoothly without stalling after starting.
