Reasons for Low Fuel System Pressure?
2 Answers
Common causes of low fuel pressure are as follows: 1. Internal blockage of the high-pressure fuel pump or malfunction of the pressure regulator. 2. The cold start solenoid valve is stuck in the normally open position. 3. Damaged fuel injectors causing excessive fuel return or significant fuel leakage into the cylinders. 4. Bends, collapses, or blockages in the low-pressure fuel line leading to poor fuel supply. 5. Faulty pressure sensor signal. 6. Damaged electric fuel pump, etc. Solutions for low fuel pressure in fuel-injected engines are as follows: 1. The fuel injector sprays fuel near the intake valve. When the engine operates and the intake valve opens, the fuel is drawn into the cylinder for combustion and power generation. When the fuel pump increases the fuel supply to the system, raising the fuel pressure in the lines, the pressure regulator automatically adjusts the fuel system pressure to ensure a consistent fuel supply to the injectors. Excess fuel in the system flows back to the fuel tank via the return line. 2. The electric fuel pump draws fuel from the tank, filters it through the fuel filter, and adjusts the pressure via the fuel pressure regulator, maintaining a fuel pressure approximately 300 kPa higher than the intake manifold vacuum. The fuel is then distributed to each cylinder's injector via the fuel rail, where the injector sprays fuel near the throttle valve based on commands from the ECU. 3. When installing a fuel pressure gauge, first depressurize the fuel system. Start the engine, disconnect the electric fuel pump relay or power plug, and after the engine shuts down, restart it 2-3 times to release the fuel pressure.
I've been driving for many years and have encountered issues with low fuel system pressure, which mainly stem from a few causes. The most common one is a weak fuel pump, where aging or wear leads to insufficient fuel suction, or the filter is severely clogged with accumulated dust and debris, blocking the fuel line. Sometimes, it's a faulty pressure regulator that can't maintain stable pressure, causing the fuel pressure to drop. Fuel line leaks are also a major issue; rubber hoses can crack or develop small holes over time, leading to fuel leakage and loss of pressure. Another often-overlooked cause is a loose fuel cap or blocked vent hole, which disrupts the internal pressure balance. When facing this problem, the car may have difficulty starting, sluggish acceleration, or even sudden stalling, which is very dangerous. I recommend promptly visiting a reputable repair shop to test with a pressure gauge and replace any faulty parts without delay.
