🔍 Key Concepts

• Radial piston hydraulic pump operation – which pistons are on the suction (return) stroke vs. discharge (pressure) stroke as the block rotates • Role of the pintle valve ports that align with the fluid inlet and outlet passages • How the direction of rotation shown by the arrow determines which piston is taking in oil and which is discharging

💭 Think About

• Trace the rotation of the cylinder block and imagine each piston’s motion against the reaction ring: which piston is moving outward and which is moving inward at the moment shown? • Look at how the shaded porting in the pintle valve connects each piston bore to either the inlet or outlet passage—where would low‑pressure return oil need to go? • Ask yourself: when oil returns to the pump (low pressure), is that associated with the inlet or outlet side of the pintle valve, and which numbered piston(s) are currently connected to that side?

✅ Before You Answer

• Identify which side of the pintle valve is clearly labeled fluid inlet and which is fluid outlet in the diagram. • Confirm which piston(s) are aligned with the inlet passage inside the pintle valve at the exact position shown. • Verify that the piston(s) you select are on the suction/return stroke, not the pressure/discharge stroke, given the rotation arrow.