There should be fuel in the tank, the engine is mechanically sound, the battery is charged, the starter rotates with sufficient frequency, the ignition system is in order, no leaks in the fuel system, fuel system contamination is excluded, the engine crankcase ventilation system is in order, electrical connections by ground (engine - gearbox - body) are present. The memory device has been interrogated for the presence of fault codes (STO).
Caution: The fuel system is under pressure! If the fuel line fasteners are to be loosened, they should be covered with thick rags to prevent fuel from splashing. Before loosening the fuel lines, they should be cleaned using cleaning agents.