Possible Causes:
1. Fuel Pump:
- Faulty Pump: Even with a new relay, the fuel pump itself could be failing. Check for noise from the pump when the key is turned to the "on" position (not starting). If you don't hear a humming sound, the pump may be shot.
- Pump Wiring: Verify that the wiring to the pump is intact and connected securely. Look for chafed wires, corrosion, or loose connections.
2. Fuel Filter:
- Clogged Filter: This is a common issue, especially if the filter hasn't been changed recently. A clogged filter restricts fuel flow to the engine.
- Location: The filter on a 944 is typically near the fuel tank.
3. Fuel Lines/Hoses:
- Blockage: Cracks, kinks, or debris in the fuel lines can impede fuel flow.
- Cracked/Leaking Hoses: Look for visual signs of damage and leaks.
4. Fuel Pressure Regulator:
- Malfunctioning Regulator: This component regulates fuel pressure to the injectors. A faulty regulator can lead to low or inconsistent pressure, causing starting problems.
Troubleshooting Steps:
1. Listen for the Fuel Pump: Turn the key to the "on" position (not starting) and listen carefully near the fuel tank. You should hear a humming sound from the fuel pump. If you don't, the pump may be faulty.
2. Check Fuel Filter: If you're comfortable, locate the fuel filter and check for visual signs of clogging. It's best to replace it as a preventative measure, even if it looks okay.
3. Inspect Fuel Lines: Visually examine the fuel lines for cracks, kinks, or leaks. Pay close attention to the area near the fuel tank and engine.
4. Test Fuel Pressure: If you have a fuel pressure gauge, you can test the pressure at the fuel rail. This will confirm if the fuel pump is delivering adequate pressure.
Additional Tips:
- Start with the simplest and most common causes: Start with the fuel filter, as it's the easiest to access and the most likely culprit.
- Work Safely: When dealing with fuel systems, always exercise caution. Fuel is flammable, and it's important to work in a well-ventilated area.
- Consider a Professional: If you're not comfortable with these checks or repairs, it's always best to consult a qualified mechanic for assistance.
Important Note: While this guide provides a good starting point, there could be other, less common causes for your fuel delivery issue. If you can't pinpoint the problem, seeking professional help from a knowledgeable Porsche mechanic is recommended.
