Owner's Problem Description
The owner of the 1997 Chevy Blazer reports intermittent starting issues. The starter engages, but the engine does not fire. During these no-start occurrences, the dashboard indicator lights are off and the fuel pump is silent. If the ignition key is left in the 'on' position for a while, the dashboard lights activate, the fuel pump engages, and the vehicle starts normally. Previous checks included fuses related to the ignition circuit, which appeared fine, but were not receiving power.
Professional Technical Analysis
The 1997 Chevy Blazer, equipped with a 4.3L V6 engine and approximately 180,000 miles, is exhibiting intermittent no-start conditions. When the issue occurs, the starter motor turns without starting the engine, and neither the dashboard indicator lights nor the fuel pump activates initially. This symptom points towards potential failures in the ignition switch or related circuits. The absence of power to the dashboard lights and the fuel pump suggests that the ignition switch may not be supplying power to the necessary circuits. This vehicle is known for ignition switch issues, particularly when subjected to wear or high temperatures, which could compromise the electrical connections. The issue could also stem from faulty relays or fusible links in the starting circuit. During successful starting attempts, verifying that the fuel pump engages and dashboard lights illuminate confirms that the ignition switch is capable of providing power under certain conditions, indicating an intermittent electrical issue rather than a mechanical failure in the fuel system. Current vehicle diagnostics should focus on testing the ignition switch output and continuity of the power supply to the dashboard and fuel pump circuits.
Possible Causes
Most common causes (ordered by frequency):
- Ignition Switch Failure: The ignition switch may fail to provide power to the dashboard and fuel pump circuits intermittently. This is common in vehicles of this age, especially with high mileage. The switch may have worn contacts, leading to unreliable electrical connections. Testing the ignition switch output with a multimeter should show continuity when the key is in the 'on' position. If there's no voltage present, replacing the ignition switch is recommended. - Dashboard lights not illuminating, fuel pump silent when key is turned on, intermittent starting issues.
- Faulty Relay or Fusible Link: A malfunctioning relay or fusible link in the starting circuit may prevent power from reaching the ignition switch or the fuel pump. Testing the relay for continuity and checking fusible links for integrity can help identify this issue. Commonly, relays fail due to overheating or age, causing intermittent power loss. - No power to dashboard or fuel pump; continuity tests on relays show open circuits.
- Poor Electrical Connections: Corrosion or loose connections in the wiring harness, particularly at the ignition switch or junction points, can interrupt power flow. Inspecting and cleaning connections with dielectric grease can enhance reliability. This issue can lead to intermittent starting problems, especially in humid climates. - Visual inspection reveals corroded terminals; intermittent electrical issues noted during previous repairs.
- Starter Motor Issues: While unlikely given the symptoms, a failing starter motor could also contribute to the no-start condition. If the starter is not drawing enough current due to a faulty solenoid or internal winding failure, it may turn but not engage the engine. Monitoring starter draw during attempts can help confirm this. - Starter turns but does not engage; testing reveals low draw during attempts.
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 - Initial Inspection: Begin with a thorough visual inspection of the ignition switch and related wiring. Check for any visible damage, corrosion, or loose connections. Ensure that the battery is fully charged and connections are clean. Verify that the fuses related to the ignition circuit are intact and receiving power by using a test light. Document any irregularities found during this inspection.
- STEP 2 - Ignition Switch Testing: Utilize a multimeter to test the ignition switch for proper output. With the key in the 'on' position, check for voltage at the output terminal. If no voltage is present, the switch is likely faulty and should be replaced. If voltage is present, check continuity to the dashboard and fuel pump circuits to ensure they are receiving power.
- STEP 3 - Relay and Fusible Link Inspection: Test the ignition circuit relay for continuity and functionality. If the relay fails, replace it with an OEM part (e.g., GM P/N 12345678). Additionally, check fusible links for integrity and replace any that are damaged. This ensures that power is reliably delivered to the ignition switch and other critical components.
- STEP 4 - Road Test and Data Logging: After addressing identified issues, perform a road test while monitoring power to the dashboard and fuel pump. Use the GeekOBD APP to log any relevant data, such as voltage readings and starting conditions. Pay attention to any irregularities during starting attempts, as this can provide insights into the effectiveness of the repairs made.
