Checking fuel pressure in the power system

The main criterion for the health of the engine power system is the fuel pressure in the fuel rail.

With insufficient fuel pressure, the following are possible:

• unstable engine operation;
• stop the engine at idle;
• increased or decreased idle speed of the crankshaft;
• poor vehicle handling (engine does not develop full power);
• jerks and dips in the engine when the car is moving.

To begin with, we recommend checking the reliability of the electrical contacts in the wiring harness blocks of the injection system units responsible for fuel supply (fuel pump, injectors).



Checking the fuel pressure in the fuel system is possible only if there is a pressure gauge with a hose for connection to the fuel line.

1. Turn on the ignition and listen: for a few seconds, the sound of the electric fuel pump should be heard. If it is not audible, check the pump power supply circuit.

WARNING: Be aware that the electric fuel pump will not turn on if there is pressure in the fuel supply system. In other words, if you previously turned on the ignition and tried to start the engine, then a serviceable electric fuel pump should have already created pressure in the system and its failure to turn on in this case is not a malfunction.

2. Reduce the pressure in the supply system (cm. «Reducing the pressure in the power system»).



3. Disconnect the fuel supply line from the fuel rail by squeezing the clamps of the coupling.

4. To check the fuel pressure, connect a pressure gauge (with a measurement limit of at least 5 kgf/cm²) between the fuel supply line and the fuel rail. With the engine idling, the pressure in the fuel line must be at least 365 kPa (3.65 kgf/cm²).

The following reasons for pressure drop are possible:

- Faulty fuel pressure regulator (installed in the electric fuel pump);



– clogged fuel filters (installed in the electric fuel pump) or the electric fuel pump is faulty;



– the compensator of pulsations of pressure of fuel is faulty (installed on the fuel rail).

For solutions to these problems, see the subsections «Replacing the fuel pressure pulsation compensator» And «Removal and installation of the fuel pump»).