What are the reasons for the plunger pump failing to build up pressure?
3 Answers
The reasons for the plunger pump failing to build up pressure are: 1. The filter on the suction line is clogged; 2. The oil level in the hydraulic tank is too low; 3. There is air leakage in the suction line; 4. The center spring of the plunger pump is broken, missing, or fatigued, preventing the plunger from returning and the other end from pressing the cylinder block against the valve plate; 5. Severe wear, poor fit, or initial poor sealing between the valve plate and the cylinder block contact surface. The plunger pump is an important device in the hydraulic system, relying on the reciprocating motion of the plunger in the cylinder block to change the volume of the sealed working chamber for oil suction and discharge. The plunger pump has advantages such as high rated pressure, compact structure, high efficiency, and convenient flow adjustment.
There are several common reasons why a plunger pump fails to build pressure. In older vehicles, the most frequent issue is wear or damage to internal pump components, such as aging plungers and seals causing oil pressure leakage, which prevents the pressure from rising. Another major problem is oil passage blockage—when the filter screen or oil suction port is clogged with debris, oil flow becomes restricted, and the pump cannot draw enough oil. Additionally, poor oil quality, such as using inferior or degraded oil with excessively high viscosity, can reduce the pump's efficiency. Air entering the system can also lead to unstable pressure, making the pump feel like it's running idle. It's recommended to first check simple things like whether the oil level is sufficient and the oil is clean, replace any faulty components, or clean the filter screen to see if the issue resolves. If you can't fix it yourself, it's best to take it to a professional repair shop for a thorough inspection to avoid turning it into a safety hazard.
There are many root causes for insufficient pressure in a plunger pump. I often encounter sealing issues, where worn or damaged seals allow oil to leak through gaps, preventing pressure buildup. System leaks are also common, such as loose fittings or cracked pipes, causing oil to escape and pressure to drop. Another issue is insufficient or contaminated oil; if the oil is too dirty and sticky, the pump can't rotate properly. Additionally, if the pressure valve is stuck due to design flaws, it affects the boosting effect. To address this, first visually check if the oil level is adequate. If the oil looks clean, continue using it and inspect whether the filter screen is clogged—try cleaning it. While driving, avoid overheating the pump, and regularly change the oil to prevent these issues. If the problem persists, have a professional use tools to test the pump's output.
