This section will show the working of the hydraulic high pressure pump which is used in the ID/DS models. The pump shown is the type used on the DS and later ID models.
Hydraulic pump The pump is belt driven by the engine. The high pressure pump consists of seven pistons operated by a swashplate. The picture displays one of the pistons. The hydraulic fluid is put under pressure by the piston. If the pressure is higher than the spring pressure the valve is opened moving the fluid under pressure into the high pressure hose towards the main accumulator. The operating pressure is approximately 175 kg/cm2 whereby throughput is around 0.6 liter/minute.
Hydraulic pump internals In case the main accumulator sphere does contain a pressure above 140 kg/cm2, the fluid is pumped round via the accumulator towards the reservoir under little or no pressure. Below this value the pump will press the fluid under pressure into the accumulator sphere (until the upper limit of 175 kg/cm2 closes the main accumulator valve). The high pressure pump construction remained the same during the production time of the ID/DS (however the early ID models did not have this type of high pressure pump. They operated on a 1 piston hydraulic pump.

Thanks to Dick Tjalkens for the show model of the hydraulic pump.