Abstract: The invention is directed to a method and an arrangement for making a tank-venting diagnosis for a motor vehicle. The underpressure in a tank-venting apparatus is measured and tank venting is inhibited when a determination is made that a test condition is satisfied according to which a check is made as to whether a threshold underpressure is exceeded during a tank-venting phase. The method ensures that a tank-venting apparatus will not be damaged by an underpressure which is too high and which can occur when the venting arrangement of the adsorption filter of the apparatus is blocked or when a shutoff valve of the venting arrangement no longer opens.

Abstract: A method for checking the operability of a tank-venting system for a motor vehicle having an internal combustion engine with a lambda controller, which system has an adsorption filter with a connecting line to a tank and a connecting line to the intake pipe of the engine which is provided with a tank-venting valve. The method is characterized in that a lean correction check is performed as soon as an operating condition with low air throughput through the engine is present. If the check determines a lean correction (.DELTA.FR) of the lambda controller which is less than a pregiven lean correction threshold value (.DELTA.FR.sub.-- SW), there is a pressure change check provided with respect to the pressure in the tank as soon as an operating condition is present with a high air throughput through the tank-venting valve. The tank-venting system is deemed to be operative if a pressure change effect of pregiven quality (.DELTA.Dp>.DELTA.Dp.sub.-- SW) is determined.

Abstract: The invention is directed to a method for obtaining a value for evaluating the performance loss of a catalytic converter with the aid of a forward signal of a forward gas probe mounted forward of the catalytic converter and a rearward signal of a rearward gas probe mounted rearward of the catalytic converter, the catalytic converter being connected to an internal combustion engine. The method includes the steps of: carrying out the method during the steady-state operation of the engine; multiplying the forward signal and the rearward signal with each other to form a plurality of products; averaging the products over a plurality of oscillations of the forward signal to obtain a mean value; and, utilizing the mean value as a value for evaluating the performance loss of the catalytic converter. This correlation method can be varied in different ways and especially in that the forward-probe signal is correlated without or with phase shift with the rearward-probe signal.

Abstract: The invention is directed to a method of checking the operability of a tank-venting apparatus for a motor vehicle having a fuel tank and an internal combustion engine including an air intake pipe. The method includes the steps of: measuring the temperature of the adsorption material with a first temperature sensor before the first regeneration of the adsorption material after a tanking operation; measuring the temperature of the adsorption material at a pregiven time point after the start of the first regeneration; forming the material temperature difference between the first and second measured values (.theta.1.sub.-- V-.theta.1.sub.-- N); measuring the temperature of the venting air close to the adsorption material with a second temperature sensor in advance of the first regeneration; measuring the temperature of the venting air at a pregiven time point after the start of the first regeneration; forming the venting-air temperature difference between the second and first measured values (.theta.2.sub.-- N-.

Abstract: A tank-venting arrangement includes: a tank; an adsorption filter connected to the tank; a tank-venting valve interconnecting the adsorption filter and the intake pipe of the engine; a control unit for driving the tank-venting valve so that it closes or opens; a pressure difference sensor for measuring the pressure difference between the pressure in the tank and the ambient pressure; and, an integrating unit for determining the time integral of the pressure difference. With this tank-venting arrangement, a simple and reliable determination can be made as to when so much fuel vapor should have been adsorbed in the active charcoal filter so that when the tank-venting valve is opened thereafter, a lean correction by means of a lambda controller can be required. If this lean correction is not made, this is an indication that the fuel flowing from the tank has not reached the tank-venting valve so that the tank-venting arrangement leaks or is obstructed.

Abstract: The invention is directed to a method of checking a tank-venting apparatus for a motor vehicle equipped with a fuel tank and an internal combustion engine having an intake pipe. The apparatus includes an adsorption filter having a venting end and an intake end, a supply line connecting the intake end to the tank and a connecting line interconnecting the intake pipe of the engine and the intake end of the adsorption filter. A tank-venting valve is mounted in the connecting line between the intake pipe and the intake end of the adsorption filter and a drive unit for actuating the tank-venting valve.

Abstract: A tank-venting arrangement includes: a tank having a tank closure; an electrically drivable check valve; an adsorption filter; connecting lines for interconnecting the above components; a difference pressure sensor which measures the pressure difference between the pressure in the tank and the ambient pressure and supplies a pressure difference signal; a comparator which, at least for a running engine, compares the pressure difference signal to upper and lower threshold values and supplies an opening signal to the check valve to open the latter when the pressure difference signal is greater than the upper threshold value and a closure signal for closing the check valve when the pressure difference signal drops below the lower threshold value; and, a detector unit which supplies an opening signal to the check valve for opening the check valve when the sensor determines a possible opening of the tank and a closure signal for closing the check valve when the sensor determines a possible closure of the tank.

Abstract: The invention is directed to a method of checking the tightness of a tank-venting apparatus for a motor vehicle having a fuel tank and an internal combustion engine including a lambda controller and an air intake pipe. The tank-venting apparatus includes an adsorption filter, a supply line interconnecting the adsorption filter and the fuel tank, a connecting line interconnecting the adsorption filter and the intake pipe and a tank-venting valve mounted in the connecting line between the adsorption filter and the intake pipe. The method includes the steps of: measuring the pressure difference between pressure in the tank and ambient pressure; when the tank-venting valve is opened, determining whether the pressure difference increases above a threshold value and whether a lean correction by the lambda controller is required; and, drawing the conclusion that the tank-venting apparatus leaks when neither a lean correction is determined nor the pressure difference exceeds the threshold value.