Experiencing cold start problems with your 2007 Audi A4? It can be frustrating when your car struggles to start, especially after it’s been sitting for a few hours. One component often suspected in these situations is the fuel pump. Let’s dive into a common scenario with a 2007 Audi A4 2.0T Quattro and explore potential fuel pump related issues that might be causing your cold start woes.
Many Audi A4 owners have encountered a situation where, after parking their vehicle for 3-4 hours or more, the engine fails to start on the first crank. In one instance, a 2008 Audi A4 2.0T automatic S-line Quattro with 143,000 kilometers exhibited this exact problem. Despite replacing the battery and finding no fuel-related error codes, the issue persisted. A generic engine mount code was present, but nothing pointed directly to a fuel system malfunction.
One key observation was that the fuel pump should prime when the driver’s door is opened. While this wasn’t confirmed in this specific case, it’s a common expectation in many vehicles. However, when the ignition was turned on, the fuel pump could be heard priming. Interestingly, if the owner waited for the in-tank electric fuel pump to stop priming before attempting to start the engine, the car would start up normally.
Seeking solutions, online forums revealed discussions about fuel pump relays in similar Audi models, specifically the B7 A4. These relays are typically located under the ECU. In this case, accessing the relays revealed two relays (#614). Initially, neither relay produced a clicking sound when the door was opened. Swapping the relays resulted in one relay clicking upon door opening, but still no fuel pump priming sound at that stage. Crucially, with the ignition on, the fuel pump still primed, suggesting a potential relay issue or a more complex problem.
Despite replacing the timing belt kit, rear tensioner, and cam follower, and confirming no loss of power once the engine is running, the cold start issue remained. Even after purchasing a new Relay #614, the solution wasn’t guaranteed. The absence of OBDII/CANBUS or VAGCOM codes (except for the engine mount) further complicated the diagnosis. The engine would start fine if restarted shortly after being turned off, highlighting that the problem was specifically related to cold starts after extended periods of parking.
If you’re facing similar cold start issues with your 2007 Audi A4 Fuel Pump, consider these troubleshooting steps:
- Listen for Fuel Pump Priming: Turn the ignition to the “ON” position (without starting the engine) and listen carefully for the fuel pump priming sound coming from the rear of the car, near the fuel tank.
- Check Fuel Pump Relay: Locate and inspect the fuel pump relay. Try swapping it with an identical relay if available, or replace it with a new one.
- Fuel Pressure Test: A fuel pressure test can confirm if the fuel pump is delivering adequate pressure to the engine.
- Scan for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to check for any stored or pending DTCs, even if the check engine light is not illuminated. While no codes were present in the initial case, it’s always a crucial step.
While the exact cause in the original forum post remained unresolved within the text, this exploration highlights the common symptoms and initial diagnostic steps for 2007 Audi A4 fuel pump related cold start problems. Further investigation may involve checking fuel pressure regulators, fuel filters, or even the fuel pump itself. Consulting a qualified mechanic specializing in Audi vehicles is recommended for a thorough diagnosis and repair.
