Owner's Problem Description
The owner reports that their 1999 Dodge Stratus died while driving and has not started since. They previously replaced the computer, fuel filter, and crankshaft position sensor, but the issues persist. The vehicle was towed home and despite these repairs, it remains non-operational.
Professional Technical Analysis
The vehicle is a 1999 Dodge Stratus with an interference engine, which means that if the timing belt fails, the pistons can strike the valves, potentially causing significant engine damage. The owner replaced the computer, fuel filter, and crankshaft position sensor but still experiences a no-start condition. Initial diagnostics indicate that fuel and spark are present, suggesting the ignition system and fuel delivery are functional. However, the timing belt failure has likely caused bent valves. This situation typically arises in engines where proper timing is critical for valve and piston clearance. The vehicle's current condition raises concerns about engine integrity, particularly after the timing belt was replaced and the indication of a bent valve. A thorough inspection of the cylinder head and valves is necessary to assess the extent of the damage. Safety and reliability are paramount, as starting the engine in this condition could lead to further damage. Careful measurements of compression across cylinders will help identify which valves may be compromised, alongside visual inspection for any physical signs of damage.
Possible Causes
Most common causes (ordered by frequency):
- Timing Belt Failure and Bent Valves: The vehicle's timing belt has failed, causing the pistons to collide with the valves, which is typical for interference engines. This can lead to bent valves that prevent the engine from starting. Inspection of the cylinder head is necessary to assess damage. Replacement of bent valves and potentially the cylinder head may be required. - No-start condition, previous timing belt replacement, indications of bent valves from diagnostics.
- Electrical System Issues: Although fuel and spark are confirmed, there may be underlying electrical issues such as corroded connections, especially with the crankshaft position sensor wiring, which can affect the signal to the PCM and prevent starting. - Intermittent electrical issues, visual inspection of wiring and connections needed.
- Fuel System Malfunction: The fuel filter was recently replaced, but an issue with the fuel pump or fuel injectors could still exist, leading to insufficient fuel delivery to the engine. - Previous fuel filter replacement, potential fuel pump failure if pressure is not within 35-45 PSI.
- Crankshaft Position Sensor Failure: Although replaced, a faulty or misaligned crankshaft position sensor could still prevent the engine from starting by sending incorrect signals to the PCM. - Replacement of sensor, but further diagnostics needed to verify proper alignment and function.
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 - Comprehensive OBD-II Scan: Use a professional OBD-II scanner or GeekOBD APP to retrieve any stored fault codes. Look for codes related to the crankshaft position sensor, timing issues, and any misfire or fuel delivery codes. Document all findings for further analysis.
- STEP 2 - Visual Inspection and Electrical Testing: Conduct a thorough visual inspection of all wiring and connectors related to the ignition and fuel systems. Check for any signs of wear, corrosion, or damage. Use a multimeter to test the crankshaft position sensor's resistance (should be within OEM specifications) and inspect the signal output while cranking.
- STEP 3 - Compression Testing: Perform a compression test on all cylinders to assess the condition of the valves and pistons. A reading significantly below the specified range (typically 150-200 PSI for this engine) indicates potential valve damage. Document results and check for discrepancies among cylinders.
- STEP 4 - Fuel Pressure Test: Check fuel pressure at the fuel rail using a fuel pressure gauge; it should be between 35-45 PSI. If the pressure is low, further diagnose the fuel pump and filter system. Document findings and any irregularities in fuel delivery.
