Car fuel pressure regulator diesel and petrol

How to detect the fuel pressure control valve failure

The component inspection is quite laborious and is usually performed as part of the vehicle fuel system comprehensive diagnosis.

As a start. check that there is enough fuel in the tank. Then you have to check the battery voltage. since the pressure of the fuel supply is directly dependent on it. It should be 12V. After that. you need to disconnect the negative terminal from the battery. connect a pressure gauge to the fuel system. wipe off spilt gasoline. reconnect the negative terminal to the battery. and start the engine in idle mode. Then disconnect the vacuum hose from the valve. plug its end with your finger. and measure the pressure. It should be 0.25-0.35 MPa in engines with multi-point injection. and 0.07-0.10 MPa in engines with throttle body injection.

If the pressure is excessively low. squeeze the return hose. and then check the gauge readings. Increase of the pressure to normal indicates the valve malfunction. Too high measurement results also indicate its failure in the case if the throughput capacity of the return pipeline is not impaired.

When the engine has warmed up. connect a vacuum hose to the valve. The pressure should drop by an average of 0.05 MPa. If it stays at the same level. the vacuum pipeline may be clogged up. or the valve has failed.

To measure the system’s residual pressure. shut down the engine. block the fuel tank and repeat the measurements in 10 minutes. Compare the obtained values with the values specified in the vehicle technical documents. If the system pressure is below normal. you probably have to replace the fuel pressure control valve.

You may identify that the fuel pressure control valve requires to be checked by the following symptoms:

• difficult engine start;
• unstable engine operation at idle;
• loss in the power of the power unit;
• spontaneous engine stops;
• fuel leakage from the hoses which is not eliminated by tightening the clamps. or from the valve mounting seat;
• deterioration of the vehicle dynamic performance;
• increased fuel consumption;
• car jerks while driving.

Causes of the fuel pressure control valve failure

The most common reason why the fuel control valve breaks down is the natural wear of its components. For example. slackening of the spring leads to the valve loose attachment to its seat. As a consequence. fuel is supplied to the return line even at low pressure. and the engine power decreases when gaining rpms. Besides. eventually. the membrane wears out and breaks. the rubber seal loses elasticity and cracks.

Premature component destruction is provoked by using poor quality gasoline. delayed fuel filter replacement or cleaning of the tank. The dirt accumulated on the valve surface causes it to jam. and water in the fuel promotes corrosion of the valve metal components.

Replacement of the fuel pressure control valve

The component is not repairable. If it has failed. replace it. You can mount a new part on your own. First. release the pressure in the system. Only after that you can start the valve replacing procedure. The sequence of steps is as follows:

1. Start the engine and run it at idle.
2. Remove the oil pump relay. or disconnect the wire from the fuel pump so that the engine stops.
3. Restart the power unit a few times.
4. Switch off the ignition. then reconnect the relay or the electric pump wire.
5. Disconnect the vacuum hose and the fuel drain hose from the valve.
6. Unscrew the fasteners that attach the part to the rail.
7. Remove the control valve.
8. Replace the sealing ring and install a new part.