A system for delivering fuel to an internal combustion engine comprises: a fuel pump; a hydraulic motor for said fuel pump; a plurality of hydraulic pumps (100,110,115; 101,111), arranged in parallel to pump hydraulic fluid from a hydraulic fluid reservoir to said hydraulic motor; a controller in communication with said hydraulic pumps, said controller receiving inputs and programmed to: determine a commanded speed for said fuel pump; determine a priority for each hydraulic pump as a function of predetermined criteria, wherein higher priority hydraulic pumps are operated before lower priority hydraulic pumps to supply hydraulic fluid to said hydraulic motor; and select which ones of said hydraulic pumps operate to deliver hydraulic fluid to said hydraulic motor; conduits (140,145) for delivering hydraulic fluid from said reservoir to said plurality of hydraulic pumps, from said plurality of hydraulic pumps to said hydraulic motor, and then from said hydraulic motor back to said reservoir; and valves controlled by said controller to direct hydraulic fluid through said conduits characterized in that said priority being determined as a function of at least one of a count of cumulative compression strokes of said fuel pump while respective hydraulic pump speed is non-zero; area under respective pressure versus time curves when respective hydraulic pumps are operating; and area under respective current versus time curves when respective hydraulic pumps are operating. a fuel pump; a hydraulic motor for said fuel pump; a plurality of hydraulic pumps (100,110,115; 101,111), arranged in parallel to pump hydraulic fluid from a hydraulic fluid reservoir to said hydraulic motor; a controller in communication with said hydraulic pumps, said controller receiving inputs and programmed to: determine a commanded speed for said fuel pump; determine a priority for each hydraulic pump as a function of predetermined criteria, wherein higher priority hydraulic pumps are operated before lower priority hydraulic pumps to supply hydraulic fluid to said hydraulic motor; and select which ones of said hydraulic pumps operate to deliver hydraulic fluid to said hydraulic motor; determine a commanded speed for said fuel pump; determine a priority for each hydraulic pump as a function of predetermined criteria, wherein higher priority hydraulic pumps are operated before lower priority hydraulic pumps to supply hydraulic fluid to said hydraulic motor; and select which ones of said hydraulic pumps operate to deliver hydraulic fluid to said hydraulic motor; conduits (140,145) for delivering hydraulic fluid from said reservoir to said plurality of hydraulic pumps, from said plurality of hydraulic pumps to said hydraulic motor, and then from said hydraulic motor back to said reservoir; and valves controlled by said controller to direct hydraulic fluid through said conduits characterized in that said priority being determined as a function of at least one of a count of cumulative compression strokes of said fuel pump while respective hydraulic pump speed is non-zero; area under respective pressure versus time curves when respective hydraulic pumps are operating; and area under respective current versus time curves when respective hydraulic pumps are operating. a count of cumulative compression strokes of said fuel pump while respective hydraulic pump speed is non-zero; area under respective pressure versus time curves when respective hydraulic pumps are operating; and area under respective current versus time curves when respective hydraulic pumps are operating.