If the union nut is loosened at idle and the speed does not change, this means that the corresponding injector is defective. The nozzle can also be checked with a pressure gauge.
False ignitions; detonation in one or more cylinders; engine overheating; low engine power very strong black exhaust; high fuel consumption - this indicates violations in the operation of the nozzle.
Removing
Clean the outside of the injection pipe and fuel return pipes.
Remove the injection piping as a set, releasing the union nuts on the pump and injectors, holding the inlet piping and injector mounts with a wrench, without disturbing the shape of the bend.
Disconnect the fuel return hose.
Loosen the fuel return pipe nuts and remove the fuel return pipe.
Unscrew the injectors using the long socket and fold them in the same order as they were removed.
Close the nozzle holes with plugs.
At each port, replace the holder seal and nozzle seal.
Installation
Clean the nozzle holes by inserting 4 new holder seals and nozzle seals.
Install the nozzles and tighten with a force of 60 Nm without overtightening the holders.
Fit the fuel return pipes with 4 new gaskets and tighten the nuts to 40 Nm. Tighten the injection pipeline with a force of 35 Nm, holding the pipeline holders or nozzle holders with a wrench.
Attach the piping bracket.
Loosen the union nuts of the injection pipes on all nozzle holders.
Turn the engine over with the starter until diesel fuel appears at the injection pipes.
Tighten the injection pipes. Remove air from the fuel system.