Owner's Problem Description
The owner's 1992 Dodge Shadow is experiencing a fuel delivery issue, as there is no power to the fuel tank despite having spark at the ignition. The fuses are confirmed to be okay, and the Auto Shutdown (ASD) relay seems functional. However, there is a lack of power reaching the fuel pump, which prevents the vehicle from starting. The owner has tested the ASD relay connections and noted that there was a clicking sound at one point, indicating intermittent power issues. Currently, there is no clicking sound when the ASD relay is tested.
Professional Technical Analysis
This analysis pertains to a 1992 Dodge Shadow with potential electrical issues related to fuel delivery, specifically the absence of power to the fuel pump. The vehicle features a 2.2L 4-cylinder engine and has a typical mileage of around 150,000 miles. The symptoms include a no-start condition, confirmed spark at the ignition, and indications of a possible intermittent power issue related to the fuel pump circuit. The ASD relay is responsible for powering the fuel pump relay and other critical systems. With the ASD relay being operational, the next step is to verify the integrity of the wiring and connectors leading to the fuel pump. The owner has tested the ASD relay and reported intermittent clicking, suggesting a potential issue with either the relay itself or the connections. It’s crucial to ensure that voltage is present at the fuel pump harness, which should read approximately 12V when the ignition is turned on. A thorough inspection of wiring for corrosion, breaks, or shorts is necessary, especially in older vehicles like this one, which may be subject to wear and environmental damage. The current condition of the vehicle indicates a critical need for diagnostic steps to prevent further complications. Immediate assessment of the fuel pump circuit, including testing for continuity and voltage drop, will help identify the root cause of the malfunction, allowing for targeted repairs.
Possible Causes
Most common causes (ordered by frequency):
- Fuel Pump Relay Intermittent Operation: The lack of a dedicated fuel pump relay in the Dodge Shadow means that the fuel pump is powered through the ASD relay. If the ASD relay contacts are worn or if there's a poor connection, it may not consistently provide power to the fuel pump. Testing the ASD relay for proper operation under load while monitoring voltage at the fuel pump connector is critical. Replacement of the ASD relay (OEM P/N 4671215) may be necessary if intermittent operation is confirmed. - Intermittent clicking sound from the ASD relay, lack of voltage at the fuel pump connector during testing despite ASD relay being replaced.
- Wiring Issues: Given the age of the vehicle, it's plausible that the wiring harness leading to the fuel pump has corroded connections or damaged insulation. Inspections should include continuity testing of the wires from the ASD relay to the fuel pump. Any significant resistance (greater than 5 ohms) should prompt replacement of the affected wiring. This can often be overlooked but is critical in older vehicles. - Visual inspection of wiring shows signs of wear; no voltage present at the fuel pump when the ignition is on.
- Fuel Pump Failure: The fuel pump itself may have failed, which would prevent fuel from reaching the engine. Directly applying 12V to the fuel pump connector should activate the pump if it is operational. If the pump does not respond, it is likely defective (OEM P/N 4693061) and should be replaced. A common symptom of fuel pump failure is a whining noise from the tank when the ignition is turned on. - No activation of the fuel pump when 12V is applied directly; absence of whining noise from the tank.
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 Voltage Checks: Use a multimeter to check for voltage at the ASD relay output when the ignition is on. Expected voltage should be approximately 12V. If voltage is present, proceed to check the fuel pump connector for voltage. If no voltage is found, investigate wiring integrity between the ASD relay and the fuel pump.
- STEP 2 - Continuity Testing: Use the multimeter to perform continuity tests on the wiring harness from the ASD relay to the fuel pump. Any circuit with greater than 5 ohms resistance should be investigated for damage or corrosion. Repair or replace any damaged wiring as necessary.
- STEP 3 - Fuel Pump Functionality Test: Directly connect a 12V power supply to the fuel pump connector. If the pump activates, it confirms that the pump is functional, and the issue lies in the relay or wiring. If there is no response, the fuel pump is likely faulty and needs replacement.
- STEP 4 - Relay and Harness Inspection: Visually inspect the ASD relay and wiring for any signs of damage, corrosion, or poor connections. Consider cleaning connections and replacing the relay if any issues are found. This can often resolve intermittent power issues.
