Fuel injection controller for diesel engines

An apparatus for controlling a fuel injection amount in a diesel engine. An ECU (61) computes the amount of fuel to be injected from an injector (18a) based on the operation state of the engine. Ions are formed when fuel is burned in a combustion chamber (18). A glow plug (53) detects ion current, which is produced based on ions in the combustion chamber (18). The ECU (61) corrects the computed fuel injection amount according to the detected ion current to optimize the actual amount of fuel injected from the injector (18a). More specifically, the time during which the glow plug (53) detects ion current corresponds to the actual combustion time of fuel in the combustion chamber (18). The ECU (61) corrects the computed fuel injection amount such that the actual combustion time approaches the target combustion time based on the time during which the glow plug (53) detects ion current.