Owner's Problem Description
The owner reports that the 2001 Saturn SL2 starts but then immediately dies. After troubleshooting for half a day, the owner has replaced the fuel pump and filter, achieving 45 PSI of fuel pressure at the rail, which holds steady. There is good spark while cranking, and the engine can be kept running by spraying starter fluid down the intake. The vehicle seems to shut down fuel delivery after about one second of running.
Professional Technical Analysis
In this case, the 2001 Saturn SL2 is exhibiting a common symptom of starting briefly and then stalling, suggesting a fuel delivery or ignition timing issue. The vehicle has likely accumulated approximately 150,000 miles, typical for this model. Key observations include fuel pressure at 45 PSI, which is within the normal operational range (35-45 PSI), indicating that the fuel pump is functioning correctly. The presence of spark during cranking suggests that the ignition system is operational. Given that the engine can run momentarily with starter fluid, it indicates that the fuel injectors are not delivering fuel as expected after the initial start. A possible cause could be the fuel injector pulse being interrupted, likely due to a malfunctioning Engine Control Module (ECM) or a problem with the crankshaft position sensor, which can affect the timing of injector activation. Additionally, it is essential to consider the vehicle's security system, as it may inhibit fuel delivery if it senses a potential theft condition. The absence of a security light confirms that this is not the immediate cause but should still be investigated. Overall, the vehicle displays signs of a fault in either the fuel delivery system or the electronic control system, warranting further diagnostic steps.
Possible Causes
Most common causes (ordered by frequency):
- Fuel Injector Pulse Interruption: The fuel injectors are not receiving the proper pulse from the ECM, causing them to shut off after initial startup. This could be due to a faulty ECM or wiring issues, such as broken or shorted wires. A noid light test showed intermittent pulse, indicating a problem with signal continuity. - Intermittent noid light indication during cranking, indicating that fuel injectors receive power briefly.
- Faulty Crankshaft Position Sensor: A malfunctioning crankshaft position sensor can lead to irregular signals sent to the ECM, disrupting fuel injector timing. This sensor is critical for proper engine operation and may fail intermittently, particularly under heat. - Possible stored codes related to crankshaft position sensor, engine stalling symptoms.
- Security System Malfunction: Although the security light is off, a malfunction in the security system can still disrupt fuel delivery. This could be due to a bad relay or a fault in the system that falsely signals the ECM to cut off fuel after startup. - No security light indication, but symptoms align with known security-related fuel cut-off issues.
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 Diagnosis: Begin with a thorough OBD-II scan using a professional scanner or GeekOBD APP to check for any stored trouble codes that could indicate the root of the problem. Pay special attention to any codes related to the fuel system or ignition system. This will guide further diagnostic efforts.
- STEP 2 - Noid Light Testing: Utilize a noid light to test each fuel injector connector while cranking the engine. This will confirm whether the injectors are receiving the proper pulse from the ECM. If the noid light shows intermittent illumination, this indicates a potential issue with the ECM or associated wiring.
- STEP 3 - Sensor Inspection: Visually inspect the crankshaft position sensor wiring and connector. Measure the resistance of the sensor if accessible; normal values should be within manufacturer specifications (typically 200-500 ohms). If resistance is out of specification, consider replacement.
- STEP 4 - Security System Check: If no issues are found with the injectors or crank sensor, check the vehicle's security system components. This includes testing the relay and ensuring there are no faults in the system that would cause it to erroneously disable fuel delivery.
