Fault Analysis of Rotor Pump
VE-type rotor pumps are widely used in diesel engines due to their compact size, high speed, lightweight design, consistent fuel delivery, and low noise levels. However, these pumps also have some disadvantages, such as high precision requirements, susceptibility to piston jamming, and potential for clogging.
Common Fault Phenomena:
1) No fuel supply: The fuel injector fails to deliver fuel.
2) Unstable engine speed: The diesel engine experiences shaking or jittering.
3) Air present in the pump: This can lead to poor performance.
4) Low fuel output: The pump delivers less fuel than expected.
Reasons Behind the Issues:
1) No oil delivery from the injector:
- Injection pressure is too low, often caused by incorrect adjustment or nozzle blockage.
- Supply pressure is insufficient, typically due to severe plunger wear, pump failure, or issues with the low-pressure oil circuit. Over-tightened high-pressure tubing can cause torque buildup, which may loosen the valve when temperature rises or vibration occurs during operation, leading to a drop in hydraulic pressure.
2) Unstable engine speed:
- In VE-type rotor pumps, the spike speed is usually lower. If irregularities occur, first check if the injector is faulty, then inspect the outlet valve of a cylinder for looseness.
- A low idle speed, air in the fuel system, or valve malfunction can also result in unstable performance.
3) Air inside the pump:
- Air in the low-pressure fuel line is a common issue.
- A failed drive shaft seal can allow air to enter the system.
4) Low fuel output:
- Improper calibration after installing a new plunger can lead to reduced fuel delivery. It’s recommended to increase the fuel supply by 0.5 minutes per 100 cycles after installation.
- Severe plunger wear can cause the pump to lose idle but maintain high-speed performance, resulting in a condition known as "false car."
Fault Example:
A typical issue with the VE rotor pump is air entering the pump. Even when the low-pressure fuel system appears normal, air can still be present, causing the engine to work poorly. After driving several times over a dozen kilometers, the pump might suddenly expel air and clean out the fuel. Then, after refueling, the same problem recurs. The tank was raised, and the electric fuel pump wasn’t working. Upon investigation, it turned out that air was entering through the drive shaft seal. Replacing the seal resolved the issue.
Additionally, the accelerator lever is a common area for wear in the VE pump, often leading to leaks.
The VE pump is more complex and requires higher-quality fuel to ensure longevity. Using cleaner, better-quality diesel can significantly extend the pump’s service life.
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