What are the reasons for the forklift arm not lifting up?

[LandonFitz]

Here are the reasons why the forklift arm cannot lift up: Internal leakage in the boom cylinder: During the use of the loader, hydraulic oil contamination or deterioration causes wear and aging of the seals inside the cylinder, resulting in ineffective sealing. This leads to internal pressure leakage in the system. Since the boom cylinder is an actuator, when internal leakage occurs, part of the system pressure is diverted back to the tank through the return oil pipe, causing the boom to fail to lift or to lift weakly. Internal leakage in the work pump or spline wear: The work pump pressurizes the system through the centrifugal force generated by the impeller rotating the hydraulic oil. When the gears inside the pump wear or oil leaks, the centrifugal force produced by the pump is insufficient to raise the system pressure to the standard value, resulting in low system pressure. Additionally, when the spline on the work pump shaft is severely worn, the spline slips, reducing the rotational speed, which also leads to insufficient system pressure and the inability to lift the boom. Insufficient hydraulic oil: When the hydraulic oil in the tank is insufficient, a large amount of air is mixed into the oil being delivered to the work pump, causing the pump to run idle. This reduces the system pressure and, in severe cases, can damage the work pump. Therefore, insufficient hydraulic oil can also prevent the boom from lifting.