Owner's Problem Description
The owner reports that their 1989 Dodge Daytona does not want to start, particularly in cold weather. A recent tune-up was performed without issues. However, after having the vehicle towed to the mechanic twice, it started immediately once placed on the ground. The mechanic replaced the heat sensors, but the owner experienced the same starting problem when they took it home. It failed to start again the following morning, and when towed back, it started again immediately upon being dropped off.
Professional Technical Analysis
This analysis focuses on a 1989 Dodge Daytona experiencing intermittent starting issues, particularly in cold conditions. The vehicle is equipped with a 2.5L 4-cylinder engine and an automatic transmission, approximately 120,000 miles. The owner reports that after a recent tune-up, the car failed to start on cold mornings, while it started without issue when flatbedded to the mechanic. This indicates potential issues with cold-start components or electrical connections that may be affected by temperature and mechanical vibration. The mechanic replaced heat sensors, which suggests a focus on temperature-related issues, but the problem persists. The testing conditions when flatbedding could momentarily resolve or mask the underlying issues, indicating that the problem could be related to fuel delivery or electrical components that are temperature sensitive. Notably, the starter motor, ignition switch, and fuel pump relay can exhibit failures in cold weather, leading to a no-start condition. Safety concerns include being stranded due to intermittent failures. Current conditions suggest a need for detailed diagnostics of the fuel system and electrical connections, especially under cold conditions. It's essential to check the fuel pressure and the integrity of the electrical connections, particularly grounds and relays, which can become problematic in low temperatures.
Possible Causes
Most common causes (ordered by frequency):
- Starter Motor Failure: The starter motor may have intermittent electrical issues, particularly due to cold temperatures affecting the brushes and windings. In cold conditions, the increased viscosity of engine oil can add strain on the starter, leading to a no-start condition. Testing the starter requires a voltage drop test during cranking, which should ideally show less than 0.5V across the terminals. If the voltage drop exceeds this, the starter may be failing and should be replaced (OEM P/N 53021384, estimated cost $150-250). - Intermittent clicking sound from the starter, voltage drop test results exceeding 0.5V during cranking.
- Ignition Switch Malfunction: The ignition switch may have internal wear or poor contact, leading to inconsistent power delivery to the starter and fuel pump. This problem often becomes evident in cold weather. A proper test involves checking the voltage at the ignition switch for stability during cranking (should be above 10V). If voltage drops significantly, the ignition switch may need replacement (OEM P/N 4501457, estimated cost $50-100). - Fluctuating voltage readings at the ignition switch during cranking, occasional no-start condition when turning the key.
- Fuel Pump Relay Failure: The relay controlling the fuel pump may have intermittent issues, especially in cold temperatures. Relay failure can prevent the fuel pump from operating, leading to a no-start condition. Testing the relay involves checking continuity and operation when energized; it should click and show continuity. If it fails to do so, replacing the fuel pump relay is advisable (OEM P/N 04620482, estimated cost $30-50). - Fuel pump not engaging during starting attempts, relay clicks but does not maintain continuity.
- Cold Start Sensor Malfunction: The cold start sensor (or coolant temperature sensor) may not provide the correct signal to the PCM, leading to improper fuel metering during cold start conditions. Testing the sensor involves measuring resistance; it should be around 2-3 kΩ at 20°C. If it reads higher than expected, replacement may be needed (OEM P/N 53021374, estimated cost $30-60). - Poor starting performance, resistance readings out of spec during testing.
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: Begin with a comprehensive OBD-II scan using a professional scanner or the GeekOBD APP to check for any stored or pending trouble codes. This step is crucial as it can reveal underlying issues related to the starting system or other connected systems. Pay attention to any codes related to the ignition system, fuel system, or PCM failures.
- STEP 2 - Voltage Drop Testing: Perform a voltage drop test on the starter motor and ignition switch. During cranking, measure the voltage drop across the starter terminals; it should be less than 0.5V. Additionally, check the ignition switch voltage during cranking and ensure it remains above 10V. Document all readings for further analysis.
- STEP 3 - Relay and Fuel Pressure Testing: Test the fuel pump relay for continuity and operation. Use a multimeter to check for continuity when the relay is energized; it should click and maintain continuity. Additionally, verify fuel pressure at the fuel rail; it should be within the normal range of 35-45 PSI. If low, investigate the fuel pump operation.
- STEP 4 - Sensor Testing: Test the cold start sensor for correct resistance values. Measure the resistance at various temperatures to ensure it falls within the expected range (2-3 kΩ at 20°C). If the readings are outside the normal range, the sensor may need replacement. This step is essential to ensure proper fuel metering.
