Malfunctions in the vehicle’s fuel system can be identified by such signs as engine malfunctions, erroneous information generated by the fuel meter, increase in fuel consumption for unknown reasons, fuel smell inside the vehicle, coated spark plugs, noticeable leaks at the joints of hoses and pipes, and the damp surface of the fuel system. When diagnosing the fuel system, the experts check the serviceability of the spark plugs, traces of leaked fuel under the vehicle, the functionality of the fuel pump, the functionality of the injection nozzles, and the pressure in the fuel rail.