Analysis of the procedure of evaluation of the technical condition of a high-pressure common rail fuel pump using a test bed

Piston displacement pumps use in common rail fuel injection systems generates very high pressure, reaching even 300 MPa. Maintaining such a high pressure is possible thanks to very precise machining resulting in as little clearance between the piston-cylinder assemblies. Due to very high forces operating in the systems and relatively unfavourable lubrication conditions resulting from using fuel as lubricants, the pumps are subject to wear and consequently lose their operating parameters. The high cost of production of the pumps, resulting from their technological advancement, forced their manufacturers to introduce technologies for diagnosing and regenerating them. The diagnostics consists in removing the pump from the engine and having it verified using a test bed. The first stage consists of evaluating the pump’s flow at null pressure; follow by evaluation of its maximal delivery for the pressure of 100 MPa. The obtained values are compared to the values achieved by a new pump. The effect of negative evaluation on a test bed is the disassembly of the pump, verification of the condition of its parts and replacement of the damaged elements. The authors examined new and used pumps on a tested, aiming to determine the characteristics of delivery of a pump for various pressures. The objective of the research was to identify the actual points in the pump’s operation at which the delivery drops the most due to the wear. The highest difference in delivery was found to exist for the maximal compression pressure. The obtained results were analysed and the possibility of changing the pump diagnostics procedure with the use of a test bed was determined.