Fuel pressure regulator
The fuel pressure regulator , also called the fuel pressure regulator or system pressure regulator , is a component of gasoline engines with fuel injection . He holds the of the fuel pump subsidized fuel for the injectors at a constant pressure. In engines with manifold injection , the fuel pressure is regulated depending on the manifold pressure. This is mostly done pneumatically through a connecting line from the intake manifold to the fuel pressure regulator. Due to the constant pressure difference between the fuel system and the intake manifold, the amount of fuel injected is only dependent on the duration of the opening of the injection nozzles. In some cases, the intake manifold pressure is measured by the engine control unit and the injection time is adapted to its change; the fuel pressure is absolutely constant (against ambient pressure).
The fuel pump generates the pressure that is limited by the system pressure regulator (fuel pressure regulator). When the engine is switched off, pressure should be maintained. If it falls off immediately, there are hot start difficulties. In addition to external leaks, the cause can also be internal leaks, e.g. B. Injectors, fuel lines, pressure regulators, fuel pumps.
Working method
The fuel pump delivers the fuel to the central collecting line, to which all injection valves are connected. The working principle of the pressure regulator is similar to that of the adjustable pressure reducer ; here, too, a spring-loaded diaphragm regulates the flow rate through a valve and thus the pressure in the line to the injection valves. In the case of pressure regulators with an intake manifold pressure connection, the intake manifold pressure reduces or increases the spring load on the diaphragm and thus ensures that the fuel pressure is adjusted as required.
In the past the pressure regulator was located in the outlet of the collecting line, today it is usually located on the fuel filter and keeps the pressure at approx. 3 to 5 bar (with single point injection approx. 1.25 bar). Excess fuel used to be fed back into the tank in order to pump cool fuel from the tank through the manifold again. However, by pumping back the fuel that had been heated in the engine compartment, the remaining contents of the tank were heated up, which allowed the low-boiling fuel components to evaporate, which are required for a perfect cold start. Return-free fuel supply systems are used today; the risk of vapor lock formation is minimized by the cooler fan running on after the engine has been switched off and by the detection of hot start conditions by the engine control unit.
literature
- Hans Jörg Leyhausen: The master's examination in the automotive trade part 1. 12th edition, Vogel Buchverlag, Würzburg 1991, ISBN 3-8023-0857-3
- Max Bohner, Richard Fischer, Rolf Gscheidle: Expertise in automotive technology. 27th edition, Verlag Europa-Lehrmittel, Haan-Gruiten 2001, ISBN 3-8085-2067-1