Patent ID: 7558665

Claim:
A system for determining a critical on-time for a selected one of a plurality of fuel injectors in a fuel system for an internal combustion engine, comprising: a fuel inlet metering valve having an inlet fluidly coupled to a source of fuel, a fuel pump having an inlet coupled to an outlet of the fuel inlet metering valve, a fuel rail coupled to an outlet of the fuel pump, a pressure sensor fluidly coupled to the fuel rail and configured to produce a pressure signal indicative of fuel pressure within the fuel rail, a plurality of fuel injectors fluidly coupled to the fuel rail, and a control circuit including a memory having instructions stored therein that are executable by the control circuit to control the fuel inlet metering valve to disable fuel flow from the source of fuel to the fuel rail, to periodically sample the pressure signal, to activate the selected fuel injector for an on-time duration while inhibiting fuel injection by remaining ones of the plurality of fuel injectors, to determine from the pressure signal samples a first pressure drop in the fuel rail resulting from activation of the selected fuel injector for the on-time duration, to process the first pressure drop to determine whether or not the selected fuel injector injected fuel into the engine in response to activation for the on-time duration, and to repeatedly modify the on-time duration and then execute the periodically sampling, activating, determining and processing steps until a critical on-time is determined that corresponds to a minimum on-time duration to which the selected fuel injector is responsive to inject a discernable amount of fuel into the engine.