IDLE DIAGNOSTIC DEVICE IN AIR-FUEL RATIO CONTROL UNIT OF LPG ENGINE

PURPOSE:To easily monitor an auxiliary fuel injection amount for whether it is suited or not by outputting a signal, which shows an output change corresponding to an air-fuel ratio correction coefficient, for diagnosing whether a slow fuel amount is suited or not in an idle operation condition of an LPG engine. CONSTITUTION:A mixture of LPG and intake air through a Venturi M3 in a main fuel mixing means M4, provided in an intake passage M2, further auxiliary fuel from an auxiliary fuel injecting means M5 are supplied to an LPG engine M1. Here in an idle operation control means M9, an auxiliary fuel injection amount is feedback-controlled being based on a correction coefficient, calculated in a correction coefficient calculating means M8, so that air-fuel ratio, detected in a detecting means M7, obtains theoretical air-fuel ratio. Here for diagnosing whether an idle slow fuel amount, supplied to the Venturi M3, is suited or not, in an output part M10, an output for showing an output change corresponding to the correction coefficient is generated. Accordingly, the fuel amount can be easily monitored by connecting a simplified voltmeter or the like to the output part M10.