Method and apparatus for detecting problems in sucker-rod well pumps and for determining which type of problem occurs. A first transducer provides a signal representative of the load on a sucker-rod string and a second transducer provides a signal representative of the sucker-rod position. The load signal and the position signal are used to generate a dynagraph of rod load vs. rod position with the pump working normally. A working dynagraph is continually compared with the normal dynagraph and a working load signal is continually compared with a normal rod load signal to detect problems in the pumping system and to determine the type of problem detected if one does develop.