Abstract: A system for protecting an engine equipped with an electronically controlled fuel injection apparatus, in which a battery voltage is detected. When the detected battery voltage is smaller than a predetermined reference value, performance of the engine is degraded, and when the detected battery voltage is smaller than a reference value, that is smaller than the predetermined value, the engine is stopped.

Abstract: A fuel injection quantity control system for starting a two-cycle engine. The control system calculates an initial fuel injection quantity by correcting a basic fuel injection quantity according to a subtrahend to be applied to a time factor which is determined depending on a cranking time. The time factor is differently set for a first engine start operation and second or later engine start operation, thereby improving restart of the engine.

Abstract: A first fuel injection pulse width is provided based on engine operating conditions. The amount of fuel is necessary for one combustion stroke of the engine at one time. A second fuel injection pulse width is provided based on engine operating conditions so as to inject at one time an amount of fuel for two combustion strokes of the engine. The first fuel injection pulse width is compared with a minimum value. The first fuel injection pulse width is selected when the first fuel injection pulse width is larger than the minimum value, and otherwise, the second fuel injection pulse width is selected when the first fuel injection pulse width is smaller than the minimum value. Fuel is injected at the selected injection pulse.

Abstract: A snowmobile has an upper hood having a plurality of air intakes, an engine provided downstream of the air intakes, and an air box having an air cleaner and communicating with an inlet port of the engine. An electronic control unit is disposed in a case which is secured to an upper wall of the air box. A deflector is disposed between the air intakes and the case so as to deflect intake air from the case.

Abstract: An engine start control system wherein the engine is restarted after the engine is scavenged without supplying of fuel from a fuel injection valve by cranking only when the engine almost stops as well as when a driver wants to scavenge. The driver's intention to scavenge a combustion chamber of the engine is detected by a control switch which the driver can turn on or off or an opening degree of a throttle valve in an intake passage when the opening degree is equal to or exceeds a predetermined value.

Abstract: An ignition device intermittently produces an ignition voltage in synchronism with speed of an engine. A fuel injection control is provided for operating a fuel injector for injecting fuel. A fuel pump for supplying fuel to the fuel injector is stopped at a time after the ignition and fuel injection stop, thereby keeping fuel pressure in a fuel supply passage.

Abstract: Disclsoed is a system of protecting an engine of the type where a driving power is transmitted through a variable reduction gear ratio belt, in which when breaking of the belt is detected, control of stopping the engine is performed, or control of excessively enriching the air-fuel ratio of an air-fuel mixture supplied to the engine is performed and then, control of stopping the engine is performed.

Abstract: A crankcase temperature sensor is provided for detecting temperature of a crankcase. A low speed basic injection pulse width is provided based on the detected crankcase temperature for low engine speed. An ordinary fuel injection pulse width is provided in accordance with engine operating conditions for ordinary engine operating condition. A comparator is provided for comparing the low speed injection pulse width and the ordinary fuel injection pulse width with each other. A larger injection pulse width is determined for injecting fuel.

Abstract: An air/fuel ratio control system derives a air/fuel ratio dependent correction value for correcting a basic fuel delivery amount as a proportional-integral control value composed of a proportional component and an integral component. The proportional component is derived on the basis of an air/fuel ratio indicative signal which varies the signal level when the air/fuel ratio varies across a predetermined stoichiometric value. The integral component is derived on the basis of a basic fuel delivery amount which is derived on the basis of engine speed and an engine load.

Abstract: An automatic power interrupting system for a vehicular control circuit including a relay switch having a contact connected between a power source and the supply terminal of a control circuit and a relay coil connected with the power source, a control switch connected between the power source and the supply terminal and with the signal input terminal of the control circuit and turned on only by an external force, a revolution detector for detecting engine revolutions and a switching device for turning the relay switch on when power is supplied to the circuit and off after a predetermined time period measured after stop of the engine based on a signal from the revolution detector.

Abstract: Disclosed is a system for controlling the fuel injection quantity at the start of a two-cycle engine, in which a predetermined amount of a fuel is preliminarily injected when a key switch of the engine is turned on, the revolution speed of the engine is smaller than a reference value and the opening degree of a throttle valve takes a predetermined change pattern.

Abstract: In a multi-fuel engine which is operated on gasoline, alcohol or a mixture of the two, upon an alcohol sensor being diagnosed as being out of order, an alcohol correction factor in the injection pulse width calculation is clamped at an arbitrary value and in the case of high load operation a carburetion correction factor is incrementally increased instead of being set to a pre-recorded value for the instant load.

Abstract: A fail-detection system is designed for detecting failure of a fuel concentration sensor for monitoring concentration of one of a plurality of different types of fuels which are blended to be supplied to an internal combustion engine, which fuel concentration sensor varies output signal level depending upon the monitored fuel concentration in the blended fuels. The system comprises first means for receiving the output signal from the fuel concentration sensor for providing a monitored data associated with monitored fuel concentration, second means for providing a reference data representative of normal range of the value of the monitored data, and third means for comparing the monitored data with the reference data for detecting abnormality of the fuel concentration sensor when the monitored data is out of a predetermined relationship with the reference data.