If the fuel pressure is insufficient, the following may occur:
- unstable engine operation;
- engine stop at idle;
- reduced idle speed of the crankshaft;
- insufficient vehicle responsiveness (the engine does not develop full power);
- engine failures while the vehicle is moving.
To begin with, we recommend checking the reliability of the electrical contacts in the ECU wiring harness blocks responsible for fuel supply (fuel pump module, injectors, fuel relay and associated fuses).
The fuel pressure in the fuel system is checked using a professional pressure gauge and a hose with an original fitting for connection to the valve located on the fuel rail.
1. Turn on the ignition and listen: within a few seconds you should hear the sound of the electric fuel pump. If you cannot hear it, check the electrical circuit of the electric fuel pump.
Note: If you have turned on the ignition three times without attempting to start the engine, the electric fuel pump will not turn on again, which 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 "Loss of fuel pressure in the engine fuel system").
3. Unscrew the protective cap of the fuel pressure control nipple at the end of the fuel rail. Please note that the cap has a sealing ring. If the ring is torn or has lost elasticity, replace it or the entire cap.
Note: For clarity, the work is shown with the decorative engine cover removed.
Note: If it is not possible to use a professional pressure gauge, use a regular pressure gauge with a hose and clamp. The pressure gauge must have a measurement scale of no more than 1000 kPa (10 kgf/cm²) and a division value of no more than 20 kPa (0.2 kgf/cm²). Please pay attention to the secure connection (rolling) pressure gauge and hose.
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4. Using the metal protective cap of the tire valve, unscrew the valve core (the same as in the tire)…
Note: When unscrewing the valve, a small amount of fuel may leak out, so place a rag under the fitting beforehand.
5. …and remove it from the fitting.
6. Connect a hose with a pressure gauge to the fitting. Secure the hose to the fitting with a clamp and check that it is securely fastened. Start the engine and check the pressure on the pressure gauge. It should be 380–400 kPa (3.8–4.0 kgf/cm²).
The following are possible reasons for the decrease in pressure:
- the fuel pressure regulator is faulty;
- the fine fuel filter or fuel intake filter is clogged;
- the electric fuel pump is faulty.
7. Stop the engine and reduce the pressure in the fuel system (see "Loss of fuel pressure in the engine fuel system").
8. Disconnect the pressure gauge from the pressure control nipple, screw the valve into the nipple and install the protective cap on the nipple.