Owner's Problem Description
The owner reports that their 1995 Ford Probe has difficulty starting on cold days. After not starting for three days, the engine cranks but won't start. They checked the spark plugs and replaced one, and they can hear the fuel pump humming. However, they notice a small oil leak and a gasoline smell in the oil. They are seeking assistance to diagnose the issue.
Professional Technical Analysis
The 1995 Ford Probe with a V6 engine (approximately 150,000 miles) is exhibiting a no-start condition, particularly after sitting idle for several days, especially in colder temperatures. The owner's actions of checking and replacing one spark plug indicate a potential ignition issue, but the gasoline smell in the oil suggests fuel is contaminating the oil, likely due to excessive fuel delivery or a leaky injector. The humming sound from the fuel pump indicates it is operational, but there may be an issue with fuel pressure regulation or the fuel injector operation. Potential causes could include a malfunctioning fuel pressure regulator, leaking fuel injectors, or ignition system failures, especially considering the reported distributor issues. The fact that the vehicle cranks but does not start shows that the issue likely lies in fuel delivery or spark generation. A thorough diagnosis should include a fuel pressure test, checking injector operation, and verifying ignition spark at the plugs. Monitoring the fuel trim values using a scan tool like GeekOBD APP will provide insights into whether the engine is running rich, which could explain the fuel smell in the oil.
Possible Causes
Most common causes (ordered by frequency):
- Fuel Injector Leakage: A failing fuel injector may be leaking fuel into the intake manifold when the engine is off, causing excessive fuel to enter the oil. This condition can lead to poor starting performance and fuel dilution in the oil. Typical signs include a gasoline smell in the oil and rough running or difficulty starting. - Gasoline smell in the oil, rough idle, potential fuel pooling in the intake.
- Fuel Pressure Regulator Failure: If the fuel pressure regulator is not functioning properly, it can cause excessive fuel pressure, leading to flooding of the engine and fuel entering the oil. This can result in hard starting and poor combustion. - High fuel pressure readings, fuel smell, engine flooding symptoms, potential DTCs related to fuel pressure.
- Ignition System Malfunction: Issues with the ignition coil or distributor cap could lead to weak or no spark at the plugs, causing the engine to crank but not start. Given the history of distributor replacement, thorough inspection of the ignition components is essential. - No spark at the plugs, potential DTCs indicating ignition issues, signs of wear on the distributor parts.
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: Use the GeekOBD APP to perform a diagnostic scan of the vehicle's OBD-II system. This will help retrieve any stored trouble codes (DTCs) and freeze frame data. Pay attention to any codes related to fuel system performance or ignition system malfunctions.
- STEP 2 - Fuel Pressure Test: Connect a fuel pressure gauge to the fuel rail test port. Verify that the fuel pressure is within specifications (typically 35-45 PSI). If the pressure is too high, suspect a faulty fuel pressure regulator; if too low, check for fuel pump operation or clogged filters.
- STEP 3 - Spark Test: Remove a spark plug and reconnect it to the ignition coil. Ground the spark plug and crank the engine to check for spark. If there is no spark, inspect the ignition coil, distributor cap, and rotor for wear or damage.
- STEP 4 - Visual Inspection: Perform a visual inspection of the fuel system for leaks, especially around the injectors and fuel lines. Check the oil for gasoline contamination. If contamination is present, change the oil and filter to prevent engine damage.
