Owner's Problem Description
The owner of a 2005 Dodge Neon SXT 2.0 reports that the vehicle cranks but does not start. They have ensured that there is fuel, spark, and compression present. Recent maintenance includes changing the timing belt, water pump, cam sensor, and crank sensor, yet the engine still fails to start. Interestingly, removing the fuse relay led to a brief moment where it seemed to want to start, but ultimately, it only cranks without firing. The owner seeks assistance in diagnosing the issue.
Professional Technical Analysis
This 2005 Dodge Neon SXT 2.0, with approximately 130,000 miles, is exhibiting a no-start condition despite having confirmed fuel, spark, and compression. The owner has undertaken significant recent repairs which include the timing belt, water pump, camshaft sensor, and crankshaft sensor replacement. These components are critical for proper engine timing and operation. The symptoms suggest that while basic combustion conditions are met, a more complex issue may be at play. Given that the engine cranks but does not fire, it is important to analyze the interconnections between the ignition system, fuel delivery, and timing mechanisms. The owner noted that removing the fuse relay led to what appeared to be an attempted start, which could indicate an intermittent electrical issue or a problem with the fuel injectors. It is crucial to ensure the fuel injectors are receiving proper voltage and that fuel pressure is adequate, approximately 35-45 PSI. Additionally, if the ignition timing is off, it may prevent the engine from starting. Based on the repair history, attention should be directed towards verifying the timing alignment, inspecting the ignition coil output for proper spark intensity, and ensuring that the engine management system is functioning correctly. Current vehicle condition shows that the engine is cranking freely but fails to initiate combustion, raising safety concerns regarding potential flooding or unburned fuel in the cylinders, which could lead to further complications if not addressed.
Possible Causes
Most common causes (ordered by frequency):
- Fuel Injector Failure: Despite having fuel pressure, the fuel injectors may not be operating due to a lack of voltage or signal from the engine control module (ECM). Each injector should receive a pulse signal of approximately 12V during operation. If the injectors are not activating, this could prevent fuel from entering the combustion chamber, leading to a no-start condition. Verify injector operation with a noid light or oscilloscope to ensure they are receiving the correct signal. - Inconsistent fuel injector pulse, no power to injectors during cranking, potential stored codes indicating injector circuit issues.
- Timing Belt Misalignment: Even after replacing the timing belt, incorrect alignment of the timing marks can cause the engine to crank without starting. The camshaft and crankshaft must be synchronized correctly; if they are not, the engine will not fire despite having fuel and spark. Inspect the timing marks to ensure alignment and verify proper tension on the timing belt to prevent slippage. - Visual inspection of timing marks shows discrepancies, potential incorrect belt tension causing slippage.
- Ignition System Failure: Although the owner reports a consistent spark, the spark may not be strong enough for ignition. A weak spark can occur due to faulty ignition coil, bad spark plugs, or wiring issues. The ignition coil must produce a minimum spark voltage of 12,000-45,000 volts. Conduct a spark test using a spark tester to confirm voltage levels and inspect the condition of the spark plugs for fouling or wear. - Weak or inconsistent spark during test, burned or fouled spark plugs, ignition coil output voltage below specifications.
- ECM Related Issues: The engine control module (ECM) may not be functioning properly, which can prevent the engine from receiving the necessary signals to initiate the starting process. Check for any fault codes related to the ECM and verify the integrity of all connections. The ECM should supply a consistent signal to the ignition and fuel systems. An intermittent ECM failure may not always trigger a check engine light. - No fault codes present, visual inspection of ECM connections reveals corrosion or damage, intermittent starting 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 OBD-II Diagnosis: Begin with a thorough scan using a professional OBD-II scanner or GeekOBD APP to retrieve any stored fault codes and analyze live data. Pay particular attention to any fault codes that may indicate issues with the ignition, fuel injectors, or ECM. Verify that the fuel injectors are receiving power and that the engine management system is functioning properly.
- STEP 2 - Fuel System Check: Verify the fuel pressure at the fuel rail using a fuel pressure gauge. Ensure the pressure is within specification, around 35-45 PSI. If the pressure is low, inspect the fuel pump operation and fuel filter condition. Additionally, check for any blockage in the fuel lines that could prevent adequate fuel delivery to the injectors.
- STEP 3 - Ignition System Testing: Test the ignition coils and spark plugs for proper operation. Use a spark tester to confirm spark intensity and ensure it meets the minimum voltage requirement of 12,000-45,000 volts. Also, inspect the spark plugs for signs of fouling or wear that could affect ignition performance.
- STEP 4 - Timing Verification: Verify the timing belt alignment and ensure the timing marks are properly aligned. Check the tension of the timing belt to ensure it is not slipping. This step is critical as incorrect timing will prevent the engine from starting even with fuel and spark present.
