Owner's Problem Description
The owner reports that their 2000 Plymouth Neon won't start. They have checked for spark and fuel pressure but have not been able to identify the issue. The vehicle cranks but does not start, and there are no previous repairs noted related to the starting system. The check engine light does illuminate when turning the key but goes off during cranking. The owner is seeking help to diagnose the problem.
Professional Technical Analysis
The 2000 Plymouth Neon is equipped with a 2.0L inline-4 engine, commonly experiencing starting issues after approximately 150,000 miles. The symptoms include a non-start condition with the engine cranking normally but failing to ignite. The check engine light initially illuminates, indicating the presence of stored trouble codes. A thorough diagnostic process must involve checking for spark at the ignition coils, verifying fuel delivery and pressure (specification: 40-50 PSI) at the fuel rail, and ensuring proper injector pulse width through the use of an oscilloscope or a professional scan tool like GeekOBD APP. Additionally, a compression test should be performed to rule out mechanical failures such as low compression due to timing issues or internal engine wear. The timing marks need to be confirmed, as misalignment may cause cam and crankshaft synchronization problems, which can lead to the check engine light illuminating with specific codes (such as P0340 for camshaft position sensor issues). It is crucial to inspect the dowel pin between the camshaft and sprocket for integrity, as a broken pin may lead to late cam timing, resulting in the engine not starting. The system interconnection analysis reveals that a failure in timing synchronization directly impacts the fuel injection timing and ignition system, leading to starting issues. Current vehicle assessment indicates potential safety concerns, especially if this issue arises while driving. Documenting the electrical system behavior and mechanical symptoms during testing will provide insights into the root cause of the problem.
Possible Causes
Most common causes (ordered by frequency):
- Camshaft and Crankshaft Synchronization Issue: A broken dowel pin between the camshaft and sprocket may lead to timing misalignment. This results in the cam being late, affecting the cam sensor's output signals. Typically, if the timing is off by one tooth, the check engine light will illuminate with codes such as P0340. Dowel pin failure is common after prolonged use, particularly in high-temperature environments. - Check engine light on with possible P0340 code, timing marks appear correct but camshaft not in sync with crankshaft.
- Fuel Delivery Failure: Insufficient fuel pressure due to a faulty fuel pump or clogged fuel filter can prevent the engine from starting. Fuel pressure should be within the range of 40-50 PSI at the fuel rail. Testing the fuel pump operation and inspecting the fuel filter for blockages are essential diagnostic steps. - Fuel pressure gauge reading below 40 PSI, visible debris in fuel filter.
- Ignition System Malfunction: A failure in the ignition coils or spark plugs may lead to no spark condition. Testing the ignition coils for proper resistance (typically 0.5-1.5 ohms for primary winding) and verifying spark plug condition are necessary steps to ensure proper ignition timing and combustion. - No spark present at ignition coils during cranking, resistance measurements outside of specifications.
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 OBD-II Scan: Start with a comprehensive OBD-II scan using a professional scanner or GeekOBD APP to retrieve any stored trouble codes. Pay attention to any codes related to camshaft or crankshaft position sensors, as these will guide further diagnostics. Freeze frame data will also be valuable for understanding the conditions when the issue occurred.
- STEP 2 - Spark and Fuel Pressure Checks: Verify spark at the ignition coils by using a spark tester. Ensure that there is adequate fuel pressure at the fuel rail (40-50 PSI). If fuel pressure is below specifications, check the fuel pump operation and inspect the fuel filter. Document all readings for comparison.
- STEP 3 - Compression Test: Perform a compression test to evaluate the engine's mechanical integrity. Compression readings should be within 150-200 PSI for healthy operation. If readings are low, investigate potential issues such as valve problems or timing misalignment. Use GeekOBD APP to monitor live data during the test for additional insights.
- STEP 4 - Visual Inspection of Timing Components: Conduct a visual inspection of the timing belt/chain and associated components. Ensure that timing marks are aligned correctly. If any signs of wear, damage, or misalignment are observed, further disassembly may be necessary to inspect the dowel pin and gears. Document findings for future reference.
