Trouble phenomenon:
The engine of a 2008 Audi A6L2.0TSI sedan could not start.
Fault diagnosis and troubleshooting:
After connecting the car, connect the fault diagnosis instrument, read the oil pressure of the low-pressure part of the fuel system, and find that the oil pressure is 0. When the low-pressure fuel pump was disassembled, it was found that the fuel tank was empty. The reason is that the fuel level sensor is stuck and the fuel gauge indication is inaccurate. After adding fuel, measure the oil pressure of the low-pressure part again and find that the oil pressure is 300kPa, which is normal.
Test drive, there is still no sign of the car. Measure the ignition waveform and it is normal. After measuring the fuel injection pulse, it was found that when the starter was running, the fuel injection pulse was normal, but it disappeared quickly. This shows that the engine computer took the initiative to cut off the fuel. Further, measure the oil pressure of the high-pressure part and find that the oil pressure is 0. The analysis believes that this is because the high-pressure oil pump has a low speed when starting, and it is not easy to discharge the air that entered the oil passage when there was no oil. After removing the oil pressure sensor on the high-pressure oil rail, run the starter to fully exhaust the air in the oil passage before reinstalling it. Measure the oil pressure of the high-pressure part again and find that the oil pressure is 6.5MPa at this time, which is normal. Start the engine and start the car smoothly.
Test drive after replacing the oil level sensor, troubleshooting.