Methods and systems for evaluating whether or not a fuel amount that is greater than a threshold has been release to an engine via fuel injectors when the fuel injectors are commanded off are presented. In one example, an oxygen sensor is activated and engine cranking is prevented until a pumping current of the oxygen sensor is proportionate to a concentration of oxygen sensed via the oxygen sensor so that released fuel may be observed during engine starting.

Methods and systems are provided for indicating a restriction in a fuel system vapor recovery line. Responsive to such an indication, methods and systems are provided for taking mitigating actions such that an entirety of a vehicle fuel system and evaporative emissions system, including a fuel filler system, may be diagnosed as to a presence or absence of undesired evaporative emissions, even with the restriction in the vapor recovery line present. In this way, undesired evaporative emissions may be reduced or avoided, completion rates for such tests may be increased, and customer satisfaction may be improved.

Methods and systems for evaluating whether or not a fuel amount that is greater than a threshold has been release to an engine via fuel injectors when the fuel injectors are commanded off are presented. In one example, an oxygen sensor is activated and engine cranking is prevented until a pumping current of the oxygen sensor is proportionate to a concentration of oxygen sensed via the oxygen sensor so that released fuel may be observed during engine starting.

An example system includes a controller configured to: receive pressure information indicative of a pressure level of the pressurized fuel between an electro-mechanical valve and an engine; based on the pressure level being below a first threshold pressure, send a first signal to open the electro-mechanical valve; determine, based on the pressure information, that the pressure level is increasing upon sending the first signal; in response to the pressure level increasing, send a second signal to activate a pump; determine that the pressure level has increased to a second threshold pressure; and provide information indicating that the engine is ready for operation.

A fuel mixing occurrence detection device is provided. The device includes a fuel-type identification unit that identifies a type of fuel injected into a vehicle by comparing a fuel pump drive RPM for achieving target fuel pressure with a predetermined reference value upon starting of the vehicle. A communication unit transmits a fuel mixing occurrence to an in-vehicle controller in response to determining that the fuel mixing has occurred.

Fuel injection accuracy of gaseous fuel injectors is important for efficient engine operation. However, the performance of the injectors varies from part to part and across their lifetime, and when an injector is under performing according to its specification it is often unknown what is causing the problem. An apparatus for operating a gaseous fuel injector in an engine comprises a mass flow sensor that generates a signal representative of the mass flow rate of the gaseous fuel in a supply conduit in the engine. A controller connected with the injector and the mass flow sensor is programmed to actuate the injector to introduce gaseous fuel into the engine; determine the actual mass flow rate of the gaseous fuel based on the signal representative of the mass flow rate; calculate a difference between the actual mass flow rate and a desired mass flow rate; and adjust at least one of on-time of the gaseous fuel injector and a magnitude of an injector activation signal by respective amounts based on the difference when the absolute value of the difference is greater than a predetermined value.

A method for operating an internal combustion engine with a high pressure accumulator for a fuel injection system, includes the steps of: monitoring, in a time-dependent manner, a high pressure in the fuel injection system; conducting a check, at a high pressure-dependent starting time point, as to whether a continuous injection detection is to be carried out; and checking whether a high-pressure oscillation has occurred within an oscillation time interval prior to a starting time.

A start control apparatus of an internal combustion engine includes: a gas sensor configured to detect a gas concentration of the liquefied gas fuel in a gasified state at a position near a combustion chamber; a scavenging pump configured to perform scavenging from a position upstream of the combustion chamber to a position downstream of the combustion chamber; and a control unit configured to prohibit a start of the internal combustion engine and operate the scavenging pump when the gas concentration detected by the gas sensor before the start of the internal combustion engine is equal to or greater than a predetermined threshold value.

Methods and systems are provided for regulating evaporative emissions from a fuel system. In one example, a method may comprise spinning an engine unfueled responsive to a hydrocarbon concentration at a fresh air end of a fuel vapor canister increasing above a first threshold. The method may comprise spinning the engine to pull hydrocarbons away until a hydrocarbon concentration at a purge end of the fuel vapor canister, opposite the fresh air end, increases above a second threshold.

Methods and systems are provided for detecting leaks in an intake manifold of an engine. In one example, a method may include closing all intake valves of all cylinders of the engine during an engine shut down responsive to vacuum in the intake manifold reaching a pre-determined vacuum level. The method may further include indicating a leak in the intake manifold responsive to a change in a level of vacuum in the intake manifold after closing all the intake valves of all cylinders.