Owner's Problem Description
The owner reports that their 1997 Plymouth Voyager shuts off after approximately 20 minutes of driving. The vehicle starts again after a short wait but stalls immediately when attempting to drive. Previous repairs include replacement of the ASD relay, crank sensor, and clutch sensor, but the issue persists. The current condition is concerning as the vehicle is not reliable for short trips.
Professional Technical Analysis
The 1997 Plymouth Voyager is equipped with a 3.3L V6 engine and an automatic transmission, with an estimated mileage of 150,000 miles. The vehicle's symptoms include intermittent stalling after about 20 minutes of operation, followed by difficulty restarting. Given the extensive repair history, including the replacement of critical components like the ASD relay and crank sensor, the ongoing issues suggest potential underlying faults in the ignition or fuel delivery systems. Voltage checks on the ASD relay should reveal stable operation, with expected ranges within 12-14V. Additionally, a thorough analysis of the crankshaft position sensor's signal during operation is crucial, as failure to maintain a stable pulse can lead to stalling. The vehicle's current condition is dire, as stalling can pose safety risks, especially in traffic. Notably, Chrysler vehicles of this era can experience issues with the powertrain control module (PCM), particularly related to overheating or internal failures. Assessing the PCM's operation under various conditions can provide insight into potential faults. Furthermore, a fuel pressure test should be conducted, ensuring pressure remains within 35-45 PSI during operation. If fuel pressure drops below this threshold, it could indicate fuel pump failure or obstructions in the fuel system, necessitating further examination.
Possible Causes
Most common causes (ordered by frequency):
- ASD Relay Malfunction: The Auto Shut Down relay may fail due to internal overheating or corrosion, resulting in intermittent power loss to the fuel pump and ignition system. This leads to stalling after 20 minutes of operation. The relay should be tested for continuity and operation under load, with a voltage supply expected to be around 12V while engaged. - Intermittent starting issue, voltage drop observed at ASD relay during operation, relay shows signs of corrosion.
- Crankshaft Position Sensor Failure: The sensor may exhibit thermal failure, causing erratic signal output after the engine warms up. This is a known issue with high mileage Chrysler vehicles. The sensor should read a steady voltage of around 5V; fluctuations may indicate failure. - No-start condition after stalling, potential stored codes related to crankshaft position sensor, fluctuating voltage readings.
- Fuel Pump Failure: The fuel pump may be overheating and shutting down, leading to loss of fuel pressure. A fuel pressure test should reveal values below 35 PSI during stalling events, indicating the need for a pump replacement. - Low fuel pressure during operation, audible change in fuel pump noise, stalling immediately after starting.
- PCM Failure: The Powertrain Control Module may have internal faults, particularly in high mileage vehicles. Failure to properly control ignition and fuel delivery due to PCM issues can result in stalling. Diagnostic scans should check for PCM-related fault codes. - Stored fault codes suggesting PCM malfunctions, irregular behavior of engine parameters, overheating of PCM unit.
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 - OBD-II Scan: Start by performing a comprehensive scan using the GeekOBD APP to retrieve any stored fault codes. Pay special attention to codes related to the ASD relay, crankshaft position sensor, and PCM. Document any freeze frame data for further analysis.
- STEP 2 - Voltage Check at ASD Relay: Perform a voltage check at the ASD relay when the vehicle is running. The expected voltage should be stable at around 12V when engaged. If voltage fluctuates or drops significantly, consider replacing the relay.
- STEP 3 - Fuel Pressure Test: Connect a fuel pressure gauge to the fuel rail and check for a sustained pressure of 35-45 PSI during operation. If the pressure drops below this threshold during stalling, it indicates a failing fuel pump.
- STEP 4 - Crankshaft Position Sensor Testing: Check the crankshaft position sensor's output voltage while the engine is running. Use the GeekOBD APP to monitor the signal; it should remain steady at around 5V. If fluctuations are noted, consider replacing the sensor.
