An object of a control method to control a direct injection internal combustion engine that directly injects fuel in a cylinder is to reduce an increase in PN caused by attachment of the fuel to a fuel injection valve distal end. The control method cools the fuel before a fuel temperature when the fuel passes through an injection hole on a fuel injection valve reaches a temperature at which an amount of attached fuel to the fuel injection valve distal end increases.

A method for operating a combustion engine is provided. A fuel injector is operated to perform a fuel injection, a sequence of pressure signals of the fuel rail pressure during the fuel injection is sampled and filtered and a total pressure difference between a first sample after a top dead center of the fuel pump and before the fuel injection has started and a chosen second sample after the injection and before a next pumping stroke is determined. A linear pressure slope at the second sample and a leakage pressure difference between the first sample and the second sample based on the linear pressure slope is calculated, leading to calculating an injection pressure difference as the difference between total pressure difference and the leakage pressure difference. With this, a value of a fuel quantity injected as a function of the injection pressure difference can be determined, while leakages are compensated.

Methods and system are provided for operating a fuel system of a stop-start engine system. In one example a method may comprise powering off a lift pump and maintaining a volume control valve in a closed position during an engine stop to maintain a fuel pressure within a fuel rail and one or more fuel injectors. The method may further comprise, in response to determining an engine start is desired, powering on the lift pump, initiating cylinder combustion, and operating a higher pressure pump (HPP) in an unpressurized mode when a fuel pressure upstream of the HPP is less than a threshold and switching to operating the HPP in a pressurized mode when the fuel pressure upstream of the HPP reaches the threshold.

A low pressure fuel pump control system of a GDI engine may include a low pressure fuel pump primarily pressurizing fuel supplied from a fuel tank, a high pressure fuel pump secondarily pressurizing fuel from the low pressure fuel pump, a low pressure fuel pump pressure sensor and a high pressure fuel pump pressure sensor detecting fuel pressure of the low pressure fuel pump and the high pressure fuel pump, and a fuel supply pressure controller setting a final target pressure of the low pressure fuel pump by correcting a reference pressure, wherein the reference pressure is corrected by a low pressure correcting pressure according to temperature of the low pressure fuel pump and a correction pressure.

Various embodiments of the present disclosure relate to methods and systems for measuring an injected fuel quantity during multipulse injection events in a common rail of a fuel system including a fuel pump to supply fuel to the common rail. The method, using a control unit, determines if each of the multipulse injection events in a normal operating condition includes a pilot pulse; in response to determining that the pilot pulse is included, obtaining an enforced separation value between the pilot pulse and the main pulse to emulate a single-pulse injection; while the fuel pump is temporarily shut off, performing a temporary enforced separation on a fraction of the multipulse injection events; measuring a pressure change in the common rail during the temporary enforced separation; and resuming the normal operating condition of the multipulse injection events after the pressure change is measured.

A method and apparatus are disclosed for determining the fuel quantity that is actually injected by a fuel injector in an internal combustion engine. A fuel injector is operated to perform a fuel injection. The first discharge stroke of the fuel pump is deactivated following a start of the fuel injection for preventing the discharge stroke from delivering fuel into the fuel rail. A value of a pressure drop caused into the fuel rail by the fuel injection is calculated. A value of a fuel quantity injected by the fuel injection is calculated on the basis of the calculated value of the pressure drop.

The present invention provides a method for analyzing and optimizing the injection of fluid into an internal combustion engine via a common rail system. Once various injection parameters are determined for a given injection system, these data may be used to model the effect of sequential injection events for the system. A processer can then be used to run the model and to adjust sequential fuel injection events to optimize engine performance and fuel usage.