Disclosed is a glow plug diagnosis method of being able to diagnose the aging or fault of a glow plug without being affected by cooling associated with air intake/exhaust or fuel injection, the method including: a step (S102) of energizing a glow plug 1 in a predetermined manner when a key switch 11 of a vehicle is turned on; and a step (S106) of measuring the resistance value of the glow plug 1 when the energization of the glow plug 1 is started, and the resistance value of the glow plug when the energization of the glow plug 1 is started and then a change in the resistance value is saturated, and of calculating a change in the resistance value over time as a resistance value gradient, in which it is determined that the glow plug 1 is normal when the resistance value gradient exceeds a predetermined first gradient reference value a, and it is determined that the glow plug 1 is faulty, and a warning lamp or the like is lighted when the resistance value gradient is less than a predetermined second gradient reference value b (S112 and S118).

A method for regulating or controlling the temperature of a sheathed-element glow plug in a heating phase of the sheathed-element glow plug, where a temperature value is determined as a function of a resistance of the sheathed-element glow plug. To render possible the regulation or control of the temperature of the sheathed-element glow plug also during a transient temperature distribution within the sheathed-element glow plug, the resistance used for determining the temperature value during a transient thermal response within the sheathed-element glow plug is calculated with the aid of a physical model.

There are described methods and systems for operating a glow plug. The method comprises monitoring a glow plug current; applying a nominal voltage V.sub.N to the glow plug when the glow plug current is between an upper threshold I.sub.1 and a lower threshold I.sub.2<I.sub.1; applying a voltage V.sub.H>V.sub.N to the glow plug when the glow plug current exceeds the upper threshold I.sub.1; and applying substantially no voltage to the glow plug when the glow plug current falls below the lower threshold I.sub.2.

There are described methods and systems for operating a glow plug. The method comprises monitoring a glow plug current; applying a nominal voltage V.sub.N to the glow plug when the glow plug current is between an upper threshold I.sub.1 and a lower threshold I.sub.2<I.sub.1; applying a voltage V.sub.H>V.sub.N to the glow plug when the glow plug current exceeds the upper threshold I.sub.1; and applying substantially no voltage to the glow plug when the glow plug current falls below the lower threshold I.sub.2.

Described is a method for regulating the temperature of a glow plug of an internal combustion engine, wherein a target resistance is determined from a target temperature by means of a resistance temperature characteristic of the glow plug and the actual resistance of the glow plug is regulated to the target resistance, the glow plug is heated to determine the resistance temperature characteristic of the glow plug, and thereby determining a resistance gradient and an electrical resistance of the glow plug is measured before the heating or at a defined time during the heating, using both the measured resistance and the resistance gradient, the resistance temperature characteristic is determined.

A method for regulating the surface temperature of a glow plug is described, wherein the electrical resistance of the glow plug is continuously measured and used to regulate the surface temperature of the glow plug to a target temperature or a target resistance corresponding to the target temperature by means of a resistance temperature characteristic. According to this disclosure, it is provided that the resistance temperature characteristic used for the temperature regulation is adjusted as a function of the present motor operating state.

A control apparatus for a diesel engine includes a neighboring temperature estimating section which estimates a temperature of a neighborhood of a glow plug that heats an interior of a cylinder upon startup, and a supercharging pressure control section which controls a supercharging pressure in such a way that a rotation fluctuation of the engine does not increase, on the basis of the estimated temperature of the neighborhood of the glow plug.

A method for controlling the temperature of glow plugs of a combustion engine is described, wherein all glow plugs are heated up for an engine start by the input of electrical energy according to a profile which is uniformly specified for all glow plugs of the engine, a change in resistance R is ascertained for each of the glow plugs for at least one specified time span, and a target resistance value is calculated for each glow plug from the associated change in resistance R, this value being expected for the glow plug when it has reached its target temperature, and the target resistance value is used to control the temperature of the glow plug to the target temperature.

A method for regulating the surface temperature of a glow plug is described, wherein the electrical resistance of the glow plug is continuously measured and used to regulate the surface temperature of the glow plug to a target temperature or a target resistance corresponding to the target temperature by means of a resistance temperature characteristic. According to this disclosure, it is provided that the resistance temperature characteristic used for the temperature regulation is adjusted as a function of the present motor operating state.

Described is a method for regulating the temperature of a glow plug of an internal combustion engine, wherein a target resistance is determined from a target temperature by means of a resistance temperature characteristic of the glow plug and the actual resistance of the glow plug is regulated to the target resistance, the glow plug is heated to determine the resistance temperature characteristic of the glow plug, and thereby determining a resistance gradient and an electrical resistance of the glow plug is measured before the heating or at a defined time during the heating, using both the measured resistance and the resistance gradient, the resistance temperature characteristic is determined.