1. A method of determining impending pump failure in a multiple pump hydraulic system, comprising; measuring volumetric efficiency of the hydraulic system; determining that one of the multiple pumps is approaching failure when the volumetric efficiency is decreasing at a rate greater than a predetermined threshold; measuring pump displacement at standby for first and second pumps when it is determined that one of the pumps is approaching failure; determining which one of the first and second pumps is approaching failure when the measured pump displacement at standby of one of the pumps is greater than the pump displacement at standby for the other pump by a predetermined range; and generating a signal indicating an impending failure of the pump with the greater pump displacement at standby.