Abstract: The present invention relates to an internal combustion, reciprocating pin engine with a piston which, on its up-stroke, sucks air or a fuel-air mixture via a flap valve or a similar device into the space beneath its base and, during the down-stroke, sends the then compressed gas via another flap valve or a similar device and a connecting passage to the inlet control ports of said internal combustion, reciprocating piston engine. The pump space of the piston pump which is formed by piston, cylinder liner and annular slide comprises an inlet passage and an outlet passage, equipped with diaphragm valves, respectively.