For the stable operation of the injection engine in all modes, a constant fuel pressure in the fuel rail is required
If there is insufficient fuel pressure in the fuel rail, then there will be unstable engine idling, insufficient engine response, jerks and failures in engine operation when the vehicle is moving.
Disconnect the fuel supply line from the fuel rail.
Connect the line with pressure gauge from the test kit (Mot1311-01) to the "tee" of the instrument (Mot. 1311-08) and the fuel supply line to the "tee" of the rail pipe (fig. 1).
Scheme for connecting devices when checking an electric fuel pump: 1 - pipeline with a pressure gauge; 2 - "tee" of the device (Mot1311-08); 3 - fuel supply line
Perform the test procedure with the engine off.
Remove the cover of the Protection and Switching Unit.
Disconnect the brown connector of the protection and switching unit (see figure 2).
Connect the brown connector pin to the battery + terminal to actuate the fuel pump (see fig. 3).
Measure the pump output, which should be 80–120 l/h.
Next, check the fuel pressure in the fuel rail.
Checking fuel pressure
To check the fuel pressure in the rail, you need a pressure gauge with a set of adapters for connecting to the fuel pipeline.
If, when the ignition is turned on, you cannot hear how the electric fuel pump works, then it may have failed.
But here it must be borne in mind that the electric fuel pump turns on when there is not enough pressure in the fuel rail.
If the pressure is normal, then the electric fuel pump will not work.
To check the fuel pressure, first reduce the fuel pressure.
Fuel pressure can be reduced in many ways.
You can turn off the fuel pump relay or disconnect the connector from the fuel module, then start the engine and wait until it stalls.
Also, if the engine has not been started for 2-3 hours, then there should be no pressure in the fuel rail.
Squeeze the retainer of the fuel rail hose end
Disconnect the hose from the fuel rail
Connect the pressure gauge adapter between the supply hose and the fuel rail.
Start the engine and look at the pressure gauge.
Fuel pressure at idle must be at least 3 kgf/cm2.
If the pressure is not enough, then the following reasons for the decrease in fuel pressure are possible:
- - malfunction of the fuel pressure regulator;
- — fuel pump malfunction or contamination of the fuel fine filter built into the fuel module.