A pump housing (11,12,14) contains two chambers (19,20) mutally aligned and interconnected and a piston (8) which reciprocates in a cylinder (16) and so defines a pumping chamber (23) linked to a fuel feed (3). The piston lies open at one free end to the first chamber (19) and an externally driven drive shaft (9) rotates round its axis and mounts a co-rotating cam (10) whose rotation moves the end of the piston (8). The shaft rotates relative the husing via bearing (31) in the second chamber (20) and lubricating oil is supplied to both chambers by an oil inlet (41) open at one end to the first chamber (19), the oil led off by an outlet (42) open one end to chamber (19). The cam (19) is integrated with a guiding sector of the shaft, the sector rotated via the bearing (21). The fuel pump can be postioned so the open ends of the inlet and outlet are on the upper part of the chamber (19). The pump has first and second nonreturn valves placed in inlet and outlet respectively for inward and outward flow of the lubricating oil to and from the first chamber (19). One of the open ends of inlet and outlet lies in the bottom part of the chamber (19) and contains a nonreturn valve as well as an oil filter (56).