How to remove and install the fuel injection pressure sensor？

What is a fuel pressure sensor？

The fuel pressure sensor is also called a fuel pressure regulator, which is used to control the fuel pressure in the fuel circuit, maintain a constant fuel supply pressure from the fuel injector, and send excess fuel back to the fuel tank. Fuel pressure sensors are divided into high pressure fuel sensors and low pressure fuel sensors.

Fuel pressure sensor installation location

Low pressure fuel pressure sensor

The low-pressure fuel pressure sensor is installed in the fuel inlet line leading to the two high-pressure fuel pumps. It measures the fuel pressure of the low pressure fuel system and sends a signal to the engine control unit.

The engine control unit uses this signal to control the low-pressure fuel system. The engine control unit sends a signal to the fuel pump control unit according to the sensor signal, for it to adjust the electronic fuel pump according to the signal.

High pressure fuel pressure sensor

This sensor is used in direct injection engines. It measures the fuel pressure of the high-pressure fuel system and sends the signal to the engine control unit.

The engine control unit analyzes this signal and adjusts the pressure in the fuel distributor line through two fuel metering valves.

How to remove and install the fuel pressure sensor？

First remove the engine cover to remove the fuel pressure sensor for pressure relief operation. Unplug the fuel pressure sensor line connector.

Unscrew the screw of the front coolant pipe, and use a removal tool to remove the connecting plug from the fuel pressure sensor. Use a socket wrench to unscrew the fuel pressure sensor.

Two O-rings must be replaced when installing the fuel pressure sensor. Screw the fuel pressure sensor into the adapter with a socket wrench. Then install the fuel pressure sensor plug and the screws of the front coolant pipe. After installation, you can start the engine to run for a few minutes and check the fuel pressure sensor for leakage. Use the engine diagnostic tool to clear the engine fault.

Pay attention to the points

Maintain in a ventilated environment,avoid touch the fuel pressure sensor; wear protective gloves. Before loosening the connection position, thoroughly clean the connection position and the surrounding area.

Only clean parts are allowed to be installed: the parts can only be taken out of the package before installation. It is not allowed to use the pressure sensor without packaging. The pressure sensor is a precision instrument and cannot be contaminated.

Do not change the original direction of the wires and pipes, and pay attention to sufficient safety distance between components.

Wear protective glasses and fuel-resistant gloves when loosening the hose connection. Carefully remove the connecting tube to relieve the pressure. Dispose of residual fuel properly.

Remove and install the high-pressure fuel pump only after the engine has cooled down.

When installing the high-pressure fuel pump, be careful not to allow dirt to enter the fuel system.

The O-ring must be replaced.

For opened devices, compressed air cannot be used for work, and the vehicle should not be moved as much as possible. If repairs cannot be performed immediately, the opened parts should be carefully covered or closed.

The working principle of fuel pressure sensor

There is a pressure chamber in the fuel pressure regulator. There is a diaphragm with an overflow valve in the cavity. The pressure measurement is produced by the bending of the steel diaphragm. A polysilicon strain gauge element is placed on the diaphragm. When on the diaphragm, the diaphragm produces a micro-displacement proportional to the medium pressure, which changes the resistance of the sensor. The inner side of the diaphragm is a vacuum chamber, and there is a spring in the chamber. The pressure difference caused by the pressure of the fuel system and the vacuum of the intake pipe and the spring force act on the diaphragm together. When the pressure difference between the pressure of the fuel system and the vacuum of the intake pipe is lower than the spring force, the overflow valve closes; when the pressure difference between the pressure of the fuel system and the vacuum of the intake pipe is higher than the spring force, the overflow valve opens. Excess fuel flows back to the fuel tank through the return pipe. In this way, the pressure of the fuel system can be adjusted to maintain a constant fuel supply pressure (approximately within the range of 180-320kpa).

Symptoms of damaged fuel pressure sensor

If the low-pressure fuel pressure sensor fails, the fuel pressure is pre-adjusted instead of fuel pressure adjustment, and the engine control unit controls the fuel pressure regulating valve with a fixed value. The fuel pressure is approximately 6.5 bar.

If the high-pressure fuel pressure sensor fails, the high-pressure fuel cannot be established. The engine runs urgently at low fuel pressure. Causes power and torque loss.

If the fuel pressure sensor is damaged, it will not be able to accurately detect the fuel pressure, so that the engine cannot give the correct fuel value according to the working conditions. When EOM considers it to be a fault, it will be stored in the form of fault code 268.

Therefore, the most common phenomenon is that the oil pressure is too high or too low, causing the mixture to be too thick, leading to increased fuel consumption and black smoke from the exhaust pipe. Or there may be failures such as weak acceleration, difficulty in starting, insufficient power, and difficulty in starting the engine.

The function of the pressure regulator is to keep the pressure in the oil circuit constant. If the oil pressure is too low, the injector will spray too weak or not, and if the oil pressure is too high, the oil circuit will be damaged or the injector will be damaged.

How to troubleshoot the fuel pressure sensor

Troubleshooting methods for fuel pressure sensor: 1. Clean the fuel injector, throttle body and idle speed motor. 2. Check whether the vacuum diaphragm is broken. 3. Exhaust the mixed air and check the airtightness of the regulator.

Fuel pressure sensor detection

Check the fuel pressure/temperature sensor and engine wiring harness and ECM connector terminal for damage. If there is any damage, repair it or replace the wiring harness or sensor.

Monitor fuel pressure. During engine operation, use engine status detection software to check fuel pressure. When idling, the fuel pressure is 5000psi and the maximum fuel pressure is 15000psi. If it fails, the fuel temperature/pressure sensor should be replaced.

Clear the fault code. Start the engine, let it rotate at idle speed, and use the engine state detection software to prove that the fault code 268 no longer works and has become an inactive fault code. Connect all the components, the start switch is in the ON position, use engine condition detection software to clear the non-current fault codes, and confirm that all the fault codes have been cleared.