Questions of localization of faults in the fuel supply system with direct injection
Abstract
Direct injection system - (Gasoline Direct Injection (GDI) - a fuel supply system for gasoline internal combustion engines, in which the nozzles are located in the cylinder head and fuel is injected directly into the cylinders.Direct injection (DI) system has become widespread due to significant fuel savings , which reaches up to 20% [1]. The popularity of the system, together with the fact that its design differs in many respects from the device of its predecessors, determined the demand of the automotive public for the availability of systems diagnostics services and localizing its faults. Many variants of the system of various environmental standards, manufacturers and years of manufacture are known to date. The article sets the task, using a specific system model as an example, to show the sequence of localization steps and the required amount of preliminary information for the development and compilation of a matrix for determining faulty components of the high pressure circuit.
The mass spread of power supply systems with control units provides for wide access to maintenance and repair services, in particular, to diagnostics services. For this, OBD-2 scanners, universal and focused on specific car brands, as well as universal means of measuring physical quantities (manometers, ohmmeters, ammeters, etc.) can be involved. An important role here is played by observing the features of the engine's behavior, such as twitching, sudden loss of power, sudden stop, etc.
Features of the fuel supply system with control unit: self-diagnostics, two circuits - low pressure and high pressure. In addition, each circuits has its own closed- circuits pressure control circuits that delivers fuel on demand. This function is also supported by the control valve in the high pressure fuel pump (injection pump), which has a normal open position. The features of the system structure were used in the development of algorithms and a matrix for diagnostics. In addition, the results of observations of the behavior of the car, cause-and-effect relationships in the presence of malfunctions, and the opening of feedbacks in the circuits were taken into account. During the development of rational diagnostic algorithms, various criteria for choosing a sequence of operations are usually used: a probabilistic criterion, criteria for minimizing the complexity of the verification operation. The complex criterion was used in this case - the ratio of the probabilistic characteristics and the characteristics of labor intensity, the use of which, due to the bilateral action, can increase the efficiency of diagnostics. Preference was given to maximizing the ratio of the failure rate parameter to the labor intensity of component replacement, bearing in mind that manufacturers of cars and their electrical and electronic components, if a malfunction is suspected, recommend replacement for the time of diagnostics.
