The fuel pressure regulator belongs to the fuel supply system of the electronic control engine, and controls the fuel pressure of the injector (Generally, the pressure is about 324kPa, and the specific pressure value will be varied depending on the engine model. In the article titled how to test the fuel pressure, you can learn more about the fuel pressure). In addition, the pressure regulator acts like a check valve on a fuel pump to maintain residual pressure in the fuel line.

Working principle of the fuel pressure regulator

The fuel pressure is coordinated by the spring and gas chamber vacuum degree. If the fuel pressure is higher than the standard value, the pressure will push up the diaphragm, the ball valve will be opened, and the excess fuel will flow back into the fuel tank through the return pipe. If the pressure is lower than the standard value, the spring will press the diaphragm to close the ball valve and stop fuel return. The function of the pressure regulator is to keep the pressure constant in the fuel line. If the fuel pressure is too low, the fuel injection will be weak. If the fuel pressure is too high, the fuel line and fuel injector will be damaged.

There is a diaphragm inside the pressure regulator to control the opening and closing of the pressure valve. If the fuel pressure is lower than a certain value, the pressure in the fuel pipeline will be increased by pressurizing the fuel pump, and the pressure valve will be closed. If the pressure exceeds the specified level, the diaphragm will be opened and the over-pressured fuel will flow back to the fuel tank through the return pipeline, releasing the excessive fuel pressure.

How to check the fuel pressure regulator

(1) Check the fuel pressure regulator in working condition

Measure the fuel pressure with pressure gauge in idle state, then remove the vacuum hose from the regulator. At this time, the fuel pressure should be increased by about 50kPa. Otherwise, it should be replaced.

(2) Check the holding pressure of the fuel pressure regulator

When checking, connect the fuel pressure gauge to the fuel line, and use a wire to connect the two terminals of the electric fuel pump. Turn on the ignition and let the electric gasoline pump run for 10 seconds. Then turn off the ignition and remove the wires. After 5min, observe the fuel pressure, this kind of fuel pressure is called holding pressure. If the pressure is lower than the specified value, clamp the return line of the fuel pressure regulator. If the fuel pressure rises, it indicates a leak in the regulator and should be replaced. If the fuel pressure remains constant, it indicates a leak elsewhere in the fuel system. If the pressure is higher than the standard value, maybe the regulator vacuum hose is leaking.