What is the normal fuel pressure for a car?
2 Answers
The normal fuel pressure for a car is between 300-350kPa (the specified pressure may vary for different vehicle models). Below is relevant information: 1. There are two types of automotive fuel systems: full return systems and partial return systems. The difference is that full return systems have a return line on the fuel rail, while partial return systems do not. 2. Turn the ignition switch on (without starting the engine) to operate the electric fuel pump. The fuel pressure at this time should meet technical requirements, generally fluctuating around 0.3MPa. 3. Clamp the return hose, and the reading on the pressure gauge will be the fuel pump's maximum supply pressure. This value should comply with the vehicle's technical requirements, typically 2~3 times the working pressure, i.e., 0.5~0.75MPa.
Last time I replaced the fuel pump, I did some research and found that fuel pressure varies significantly between different vehicles. Older multi-point fuel injection cars typically have an idle fuel pressure of around 2.5 to 3.5 kg/cm², which can rise above 3.5 kg/cm² when you step on the gas. Modern direct injection engines, like Volkswagen's EA888, have much higher pressures—jumping straight to 40 kg/cm² at startup and maintaining around 6 kg/cm² at idle. During testing, pay close attention to whether the pressure spikes immediately upon cold start. If it climbs slowly, the fuel pump is definitely failing. For modified performance cars, checking the data stream is even more critical. A friend of mine flashed his ECU without adjusting the fuel pressure, and it led to fuel starvation on the highway. When measuring fuel pressure, remember that mechanical gauges are more accurate than computer readings—OBD data can sometimes be misleading.
