Checking the fuel pressure in the VAZ-2121 injection engine
We perform the work on a cold engine.
The pressure in the fuel rail is checked with a special pressure gauge, but if you don’t have one, you can use a regular pressure gauge.
We put an oil-resistant hose (with an internal diameter of 12 mm) on the threaded fitting of the pressure gauge and secure it with a clamp.
Unscrew the protective cap on the rear end of the fuel rail.
Use the wheel valve cap to unscrew the valve core from the fuel rail fitting (for clarity, we show the operation on a removed rail)
Gradually release the fuel pressure and remove the valve.
Put the pressure gauge hose on the fuel rail fitting and secure it with a clamp.
Start the engine and while it is running idle, check the fuel pressure, which should be 2.8–3.2 bar (2.8–3.2 atmospheres)
Remove the vacuum hose from the fuel pressure regulator.
If the regulator is in good working order, the fuel pressure should increase by 0.2–0.7 bar (0.2–0.7 atmospheres).
If the regulator is faulty, see below how to replace it.
Removing the fuel pressure regulator
We carry out the work on a cold engine.
Disconnect the negative cable from the battery.
Disconnect the vacuum hose of the fuel pressure regulator from the receiver.
Using a 17 mm wrench, unscrew the drain pipe nut, gradually releasing the pressure.
Hold the hose fitting with a wrench of the same size.
The connection of the hose and tube is sealed with a rubber ring
Using a Phillips screwdriver, unscrew the clamping screw strips
Removing the strip
We loosen it with a 24 mm wrench nut securing the drain pipe to the pressure regulator.
Using a 5 mm Allen key, unscrew the two screws securing the fuel pressure regulator to the rail.
Separate the regulator from the ramp
Unscrew the nut and remove it.
The connection between the rail and the regulator is sealed with a rubber ring. In photos 6–10, the receiver is removed for clarity
The connection of the fuel pressure regulator to the tube is sealed with a rubber ring
We install the regulator in the reverse order
If necessary, change the sealing rings and lubricate them with engine oil.
The tightening torque of the regulator mounting screws is 8–11 Nm, and the drain tube mounting nuts are 20–34 Nm.