High-pressure pumps are the most important components of modern fuel injection systems. A modern system is the common rail one, equipping vehicles with a diesel or a gasoline engine. Depending on the fuel type, the design of the pumps is completely different, and it is more complex for diesel engines that are more prone to wear. The components subjected to wear are those in contact and continuous motion like drive shaft with roller and shoe, plunger and hydraulic head assembly with valves. Wear is initiated as a result of a process and product deviations or inadequate exploitation of the high-pressure pump. The factors influencing the wear can be improper material hardness, improper coating, incomplete or wrong machining, wrong clearance or misalignment between components, inadequate surface finish, dimensions out of tolerances, wrong assembly process, poor lubrication, contamination or running at high loads and temperatures. Our paper aims to identify, describe and discuss the types of wear encountered at common rail high-pressure pumps, highlighting the effects on their functionality. The wear occurrence can be prevented by paying more attention to the design details, manufacturing processes and correct exploitation of the high-pressure pumps.

Common-rail fuel injection systems are still a good option for equipping new car models. The technology is well known, systems of this type are reliable and can be used on a wide variety of diesel and petrol engines. However, there is still room for improvement. The ball check valve, which is part of the common-rail pump, is designed to open and allow the compressed fluid to be sent to the high-pressure accumulator and close to not allow fuel to return to the compression chamber. The valves’ design directly influences the volumetric efficiency of the outlet flow and the robustness against high pressures that lead to low performance and short service life of the fuel injection systems. This paper aims to compare two ball check valves with conical and spherical seat designs. The analysis is based on theoretical calculations and CFD simulations, which will give more confidence in the results. Considering the comparative analysis results, the ball check valve with a spherical seat shows better flow dynamics than the ball check valve with a conical seat. In addition to the improved flow dynamics, the ball check valve with spherical seat seems to have a uniformly distributed fluid pressure inside the valve. In contrast, the conical seat ball check valve has high local fluid pressures, leading to fatigue.

The service life for the assemblies represents a key factor when it comes to the product robustness. The concern for this factor starts from the beginning of each component manufacturing process. The parameters of the assembly process must be very well established, so that a compact, functional and reliable product to be the result. Thus, the existence of a testing step in the process is indispensable for the proper product functionality checking. Performing of the test procedures that simulate the components operation under certain conditions can take long period of time. This is caused by the multitude of the parameters that must be perfectly adapted according to the product operating capacity. In order to highlight these, our paper performs a comparative analysis between two automotive high-pressure pumps, using two special tests. After testing the two pumps, we noticed that the first one completed the test successfully and the second one failed the test. The purpose of this exercise is to demonstrate that the operating limits of an assembly must be precisely set. Also, a small deviation from the test parameters can lead to the total pump malfunction.

The wear of the high-pressure pump is directly proportional with the engine operating mode of the vehicle. Due to the urban areas congestion, the engine assembly components can be affected and they can lose their reliability. The engine operation can be described as a cyclical model, reaching all the operating points: idle, cranking, maximum torque and maximum power. Thus, the discontinuous operation (proportional with car engine cycles) of the high pressure pump can create different types of wear for its components. Our paper presents an experimental test that simulates the behaviour of the pump after the operation of the vehicle in urban regime with a cyclical type in a course of 10.000 km. It aims to achieve the most important engine operating points. In order to do this, an electronic control unit is installed on the test machine, which has the role of controlling the electronic pump valve. All data (pressure, speed, temperature) are recorded in real time and stored in the memory unit of the test machine. The obtained data are analyzed and the pump is disassembled. Wear is observed on the main components (roller, shoe and driveshaft), but this does not lead to pump malfunction. After this analysis, the main components of the tested pump are compared with new components in order to evaluate the wear level.

The wear analysis is a basic step for assessment of the functioning of mechanical systems and helps to the products improvement. The service life of the assemblies is approximate depending on the level of wear of their components. Starting from the product prototype phase, all components are tested and very carefully analyzed. This kind of analysis depends on the fault type and also the analysis devices are chosen in view of this. The Scanning Electron Microscope is one of the most used equipment which provides images with very good resolution at nanometers sizes. The classic microscopes are very often used for surface analysis or measurements. Hardness tester and adhesion measurements devices help to evaluate the material hardness and coatings adhesion. The improvement of the wear analysis methods is necessary due to continuing evolution of the materials and production processes. This paper presents the most common wear types from the injection high-pressure pumps and their analysis methods.