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 certain limitations, such as high precision requirements, susceptibility to piston sticking, and other operational challenges. Common Fault Phenomena: 1. No fuel supply, meaning the fuel injector is not receiving fuel. 2. Unstable engine speed, resulting in diesel engine shaking or vibration. 3. Air present inside the pump, which can disrupt fuel flow. 4. A reduced amount of fuel being delivered. Analysis of Causes: 1. **No Fuel Delivery** - Low injection pressure: This can be caused by improper adjustment or clogged nozzles. - Low supply pressure: Often due to severe plunger wear, pump malfunction, or blockage in the low-pressure oil circuit. Over-tightened high-pressure tubing can cause torsional stress, leading to valve loosening when the engine heats up or vibrates, which may result in a drop in hydraulic pressure. 2. **Unstable Engine Speed** - In engines equipped with VE-type rotor pumps, the speed fluctuation is typically less than that of traditional pumps. If irregularities occur, check if the fuel injector is faulty, and then inspect whether the outlet valve of one cylinder is loose. - Low idle speed, air in the fuel system, or valve failure can also lead to instability. 3. **Air Inside the Pump** - Air in the low-pressure oil circuit. - Failure of the drive shaft seal, allowing air to enter the system. 4. **Low Fuel Output** - Improper adjustment: After some time, a new plunger may lose its calibration, so it's recommended to increase the fuel supply by 0.5 minutes per 100 cycles after assembly. - Plunger wear: Severe wear can cause the engine to lose idle but maintain high speed, often referred to as "false car" or "false running." Fault Example: A common issue with VE-type rotor pumps is air entering the pump. Even when the low-pressure oil system appears normal, air may still be present, causing intermittent fuel delivery problems. For example, after driving a dozen kilometers, the engine might suddenly release a burst of air, followed by clean fuel being pumped. This cycle repeats, especially when the tank is high and the electric fuel pump is not functioning. After investigation, it was found 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 VE-type pumps, often leading to leaks in that region. Due to their complexity, VE-type fuel pumps require higher-quality diesel to ensure longer service life. Using clean, well-settled diesel can significantly improve performance and reduce maintenance issues. Regular inspection and proper maintenance are essential to keep the pump operating efficiently.

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