The main indicator for determining the serviceability of the engine fuel system is the fuel pressure in the fuel rail.
If the fuel pressure is insufficient, the following malfunctions may occur:
- unstable engine operation;
- engine stop at idle;
- increased or decreased idle speed of the crankshaft;
- poor vehicle responsiveness (the engine does not develop full power);
- jerks and dips in engine operation when the vehicle is moving.
To begin with, we recommend checking the reliability of the electrical contacts in the wiring harness pads of the injection system units responsible for fuel supply (fuel pump, injectors).
The fuel pressure in the fuel system can only be checked with a pressure gauge with a hose and an adapter for connecting to the fuel rail. Moreover, the pressure gauge can be connected to the fuel rail in two ways: either in the break of the fuel supply line, disconnecting it from the rail fitting...
...or to a special diagnostic connector, the design of which is similar to the design of a tire valve. Since the connection to the diagnostic connector does not require any explanation (all you need is for the tip of the pressure gauge hose to be similar to the tip of the tire pump hose), this subsection describes connecting a pressure gauge to a break in the fuel supply line as more labor-intensive and requiring additional operations.
1. Turn on the ignition and listen - you should hear the sound of the electric fuel pump for a few seconds. If you do not hear the sound of the electric fuel pump, check the electric circuit of the pump.
NOTE: If you have turned on the ignition three times without attempting to start the engine and the electric fuel pump does not start working again, this is not a sign of a malfunction. It will turn on simultaneously with the starter starting the engine.
2. Reduce the pressure in the fuel system (see "Reducing pressure in the fuel system").
3. Slide the retainer of the fuel supply line hose tip connected to the fuel pulsation compensator.
4. Press the release button...
5. ...and disconnect the hose tip from the fuel pulsation compensator fitting.
NOTE: Some fuel may leak when you remove the hose. Wipe it off with a rag.
6. To check the fuel pressure, connect a pressure gauge with a measurement range of at least 500 kPa to the gap between the fuel hose and the fuel pulsation compensator fitting.
7. Start the engine. With the engine idling, the pressure in the line should be about 380 kPa.
The following are possible reasons for the decrease in fuel pressure:
- the fuel pressure regulator is faulty (installed in the fuel module);
- the fuel filter is clogged (installed in the fuel module);
- the fuel pump is faulty.
8. Stop the engine and reduce the pressure in the fuel system (see "Reducing pressure in the fuel system").
9. Connect the fuel hose to the fuel pulsation compensator.