Owner's Problem Description
The owner reports that the engine of their 1989 Plymouth Voyager was running fine until they pressed a button on the radio, after which the engine quit. A green LED light labeled 'Fuel Purge' on the instrument panel went out. They are uncertain if the radio button caused the issue. Currently, the vehicle does not start, but there is spark. The owner has checked the fuel line and is in the process of measuring fuel pressure.
Professional Technical Analysis
The 1989 Plymouth Voyager is equipped with a 3.0L V6 engine and utilizes a Throttle Body Injection (TBI) system. The vehicle has approximately 150,000 miles. The reported issue of a no-start condition following the operation of the radio button suggests a potential electrical fault or a failure in the body control module (BCM) affecting fuel delivery or ignition signals. The owner noted that the engine had quit abruptly, which may indicate an interruption in power supply to essential components. The 'Fuel Purge' LED indicates that the fuel system is not pressurizing correctly, which is corroborated by the owner's observation of low fuel pressure readings (12-13 PSI) as opposed to the required 13.5-15.5 PSI for TBI systems. This insufficient pressure suggests a failure in the fuel pump or a clog in the fuel lines or filter. Notably, the flickering pressure during cranking indicates an intermittent fuel supply issue. The presence of spark confirms that the ignition system is functioning; however, without adequate fuel pressure, the engine will not start. Recommendations include checking the fuel pump operation and inspecting the fuel filter and lines for blockages. Additionally, verifying the integrity of the wiring and connections associated with the BCM could reveal faults contributing to this no-start condition.
Possible Causes
Most common causes (ordered by frequency):
- Fuel Pump Failure: The fuel pump may not be delivering adequate pressure due to internal wear or electrical faults. A TBI system requires fuel pressure to be between 13.5-15.5 PSI. The observed pressure of 12-13 PSI, accompanied by fluctuations, indicates potential pump failure or restriction in the fuel line. Testing the pump's voltage and ground connections is critical to ascertain if the pump is receiving proper power. - Insufficient fuel pressure readings, fluctuating pressure during cranking, and potential noise from the fuel pump not operating.
- Fuel Filter Blockage: A clogged fuel filter can restrict fuel flow, resulting in inadequate fuel pressure at the injectors. If the filter is partially blocked, it may allow some fuel to pass but not enough to meet the operational requirements of the engine, particularly under load. This would cause symptoms consistent with the owner's report of no start despite spark. - Vehicle history of fuel filter replacement, presence of debris in the fuel system, and low pressure readings.
- Body Control Module (BCM) Malfunction: The BCM controls multiple vehicle functions, including fuel pump activation. If the BCM is faulty, it may not trigger the fuel pump relay, leading to a no-start condition. This can be diagnosed by checking for power at the fuel pump relay and confirming BCM functionality through diagnostic scans. - Inconsistent operation of electrical components, BCM-related fault codes, and lack of power to fuel pump relay.
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: Utilize a professional OBD-II scanner or GeekOBD APP to retrieve any stored fault codes that may provide insight into the no-start condition. Check for BCM-related codes or fuel system errors. This initial data will help narrow down the potential issues affecting the vehicle.
- STEP 2 - Fuel Pressure Testing: Connect a fuel pressure gauge to the fuel rail test port and turn the ignition to the 'ON' position without starting the engine. The pressure should be within the specified range of 13.5-15.5 PSI. If the pressure is below this range, further investigation of the fuel pump and filter is warranted.
- STEP 3 - Voltage Check at Fuel Pump: With the ignition on and the fuel pressure gauge connected, check the voltage at the fuel pump connector. The voltage should be around 12V. If there is no voltage, inspect the wiring and connections leading to the fuel pump and check the BCM operational status.
- STEP 4 - BCM Functionality Test: If previous steps indicate no fuel delivery, utilize diagnostic equipment to test the BCM functionality. This may involve checking for outputs to the fuel pump relay and ensuring that no fault codes related to the BCM are present. If necessary, replace or reprogram the BCM based on diagnosis.
