The main reasons for the lack of pressure in plunger pumps include the following:

1. Blockage of the suction line filter: This can cause the hydraulic system to malfunction, resulting in the pump being unable to generate pressure.

2. Low oil level in hydraulic oil tank: Low oil level can affect the normal operation of the hydraulic system, causing the pump to be unable to generate pressure.

3. Leakage in the suction pipeline: Leakage can affect the normal operation of the pump, resulting in the inability to generate pressure.

4. The center spring of the plunger pump is broken, missing or fatigued: This will prevent the plunger from returning, resulting in the pump being unable to generate pressure.

5. The contact surface between the oil distribution plate and the cylinder body is severely deformed: poor sealing or initial poor sealing can cause the pump to be unable to generate pressure.

6. Severe wear between the outer diameter of the plunger and the cylinder bore: This can lead to severe oil leakage, low driving force, and thus affect the pressure output of the pump.

7. Variable mechanism R angle too small: This will result in a low flow rate, coupled with the influence of internal leakage, making it impossible to continuously supply external pressure oil.

8. Loose spring adjustment of the control variable mechanism: This can cause the flow rate to quickly decrease and pressure to be difficult to establish.

The methods to solve these problems include:

1. Clean or replace the filter on the suction line to ensure that the hydraulic system is working properly.

2. Check and replenish the oil level of the hydraulic oil tank to ensure that the oil level is within the appropriate range.

3. Check and repair the air leakage problem in the suction pipeline.

4. Replace or repair the center spring of the plunger pump.

5. Adjust or replace the seals between the oil distribution plate and the cylinder block to ensure good sealing.

6. Repair or replace severely worn plungers and cylinder chambers.

7. Adjust the R-angle of the variable mechanism to ensure sufficient flow.

8. Adjust the spring of the control variable mechanism to ensure appropriate pressure is established.

Working principle and common troubleshooting methods of plunger pump:

The plunger pump relies on the reciprocating motion of the plunger in the cylinder to change the volume of the sealed working chamber, achieving oil suction and pressurization. Common troubleshooting methods include checking and cleaning the filter, checking the oil level, repairing air leaks, replacing or repairing springs, adjusting seals, etc.