Combustion engine with fuel pump

The engine (1) has an inner crankshaft (35) present in a crankshaft housing (25), which has a combustion chamber (5) defined by a lifting cylinder (3). A crankshaft flange (37) is engaged with a drive element of a fuel pump e.g. high pressure fuel pump, of a fuel treatment device, where a drive plane of the fuel pump runs via the crankshaft flange. The fuel pump comprises a lever introduced between a crankshaft flange tap and a pump housing core. A drive exerts pump power on a pump piston of the pump. The pump is arranged in axial orientations, which deviate from a crankshaft axis. The high pressure fuel pump is selected from a diesel high pressure pump or a petrol high pressure pump. An independent claim is also included for a method for operating a reciprocating piston engine.