1、固定式升降貨梯液壓泵輸油量不足，包括固定式升降貨梯液壓泵泵油量不夠，吸油阻力過大，吸油管道漏氣，油液黏度過大或油溫太低，油箱中油面高度過低以及油箱通氣孔堵塞。
Stationary hydraulic cargo lifter insufficient amount of oil, including fixed cargo lifter hydraulic pump enough oil, oil resistance is too large, oil pipeline leaks, oil viscosity is too large or too low oil temperature, oil tank surface height is too low and a fuel tank vent clogged.

2、固定式升降貨梯液壓泵內泄漏嚴重，如零件磨損過大、密封問隙變大、泵體因鑄造缺陷等，使壓油腔和吸油腔連通。
Fixed cargo lifter pump leak serious, such as too much wear and tear parts, seals ask gap becomes larger, the body due to casting defects, so that the pressure oil chamber and the suction chamber in communication.
  
3、固定式升降貨梯壓力油路的管接頭及各種閥的泄漏，如固定式升降貨梯液壓缸、液壓馬達的密封裝置損壞，引起內泄漏嚴重。
Fixed cargo lifter pressure oil leakage of various valves and fittings, such as fixed cargo lifter hydraulic cylinder, hydraulic motor seal damage, causing severe internal leakage.