The present invention relates to a method for checking the functionality of a first pump arranged in a fuel feeding system of an internal combustion engine system, said internal combustion engine system comprising an internal combustion engine with injectors for injecting fuel into cylinders of the combustion engine and in the fuel feeding system a main fuel tank, a catch tan k, a said first pump configured to pump liquid fuel from the main fuel tan k to the catch tank and a further second pump configured to pump fuel from the catch tank to said injectors, as well as a said internal combustion engine system.

The invention is not restricted to such methods carried out for any particular type of internal combustion engine or fuel , but diesel and ethanol may be mentioned by way of examples. Furthermore, the invention relates to such internal combustion engine systems for any type of use, such as industrial applications, in grinding machines and all types of motor veh icles, although the invention is particularly applicable to utility veh icles, especially wheeled utility vehicles, such as trucks or lorries and buses, wh ich is the reason for in some parts below discussing this use for illuminating the invention but in no way restrict it thereto. Said first pump is advantageously an electric pump, but it may also be a mechan ical pump. The components of the fuel feeding system mentioned above are part of a low pressure part of this system and said second pump will pump fuel to said injectors through a h igh- pressure part of the fuel feeding system . This high-pressure part has noth ing to do with the present invention and may have an arbitrary design .

A fuel feeding system with a catch or intermediate tank arranged in the fuel feeding path between the main fuel tan k and said high- pressure part has a number of advantages. An arrangement of a said catch tank, which normally has a considerably smaller volume than the main fuel tank, is particularly interesting in motor veh icles, which may be wheeled , such as trucks and buses, or for in- stance running on caterpillar treads, such as different types of construction machines, since such a catch tank makes it possible to drive the vehicle to a position in which less fuel is left in the system than wou ld be the case when on ly having a main fuel tank, since the vehicle has to then be stopped for refueling before the fuel level in the main fuel tan k is that low that a pump connected thereto may not feed fuel out thereof when the motor vehicle is standing on horizontal ground .

The performance of a said first pump, especially when this is an electric pump, may vary due to manufacturing tolerances and aging effects, such as cavitation , wear and others. This makes it beneficial to have some way of estimating the performance/efficiency, i.e. the functionality, of such a first pump online during operation or offline in a workshop, which is what the present invention aims to obtain. SUMMARY OF THE I NVENTION

The object of the present invention is to provide a method and a system of the type defined in the introduction solving the problem mentioned above.

This object is with respect to the method obtained by providing such a method with the features listed in appended claim 1 .

Thus, by stopping the operation of the first pump thereof and then start the operation while driving the pump at a fixed number of revolutions per minute again and measuring the increase of fuel in the catch tank and how much fuel is leaving the catch tan k during a certain period of time the flow out of the pump may be determined . When a value of the flow out of the pump has been obtained this may be compared with an ideal flow out for determining the performance of the pump. This information may then be used to carry out maintenance work, replacement of components of the pump or the entire pump or taking other measures. Said amounts determined by the measurements may be in the form of mass or volumes of fuel.

According to an embodiment of the invention said start of the catch tank is in step c) determined by measuring the amount of fuel injected into the cylinders by the injectors from the time of stopping operation of said first pump in step a) and su btracting this amount from the value of the content of the catch tan k measured at the time of stopping the operation of said first pump in step a) . This measurement may then be carried out by accumulating the amount of fuel injected in every injection into cylinders of the engine from the time of stopping the operation of the first pump to the time of starting it again . This amount of accumu lated fuel is assumed to be known in the engine management system of the internal com- bustion engine system in question .

According to another embodiment of the invention the amount of fuel leaving the catch tank is in step d) measured by measuring the amount of fuel injected by said injectors into the cylinders as of said starting time. Thus, the amount of fuel leaving the catch tan k during said duration is also obtained by measuring the accumulated amount of fuel injected in every injection during the period of time in question . This means that no extra fuel measuring sensor is needed for carrying out said measurements, although it wou ld in principal be possible to have an extra sensor for obtaining this.

According to another embodiment of the invention the content of the catch tank is recorded when the operation of said first pump is stopped in step a) and the value of th is content is then in step e) used as said certain stop content. To use the content value obtained when the operation of the pump is stopped as the content value to be obtained after starting the pump again will simplify the method .

According to another embodiment of the invention the content of fuel in the catch tank is measured before the stopping of operation of said pump in step a) and the first pump is operated to obtain a predetermined value of said content to be used as a said stop con- tent in step e) to carry out step a) when this content value is reached . Said predetermined value does then correspond to a certain level of fuel in the catch tank being higher than catch tank fuel levels during normal operation of the internal combustion engine system, so that it will be enough to have one single fuel level sen- sor in the catch tan k reacting upon reaching of this certain level by the fuel in the catch tan k for carrying out catch tank fuel content measurements when carrying out the method according to the present invention . According to another embodiment of the invention the method is carried out on an internal combustion engine system of a motor veh icle, such as a wheeled motor vehicle, especially in the form of a truck or a lorry or a bus. The object of the present invention is with respect to the internal combustion engine system obtained by providing such a system with the features listed in the characterizing part of the appended claim directed at such a system. The advantages and advantageous features of such a system and the embodiments thereof de- fined in the dependent claims appear clearly from the above discussion of the method and the embodiments thereof accord ing to the present invention .

The invention also relates to a computer program , a computer readable medium, an electron ic control unit and a motor vehicle according to the appended claims directed thereto.

Further advantageous features as well as advantages of the present invention will appear from the description following below. BRI EF DESCRI PTI ON OF TH E DRAWI NGS

With reference to the appended drawings, below follows a specific description of an embodiment of the invention cited as an example.

In the drawings:

Fig . 1 is a simplified schematic view showing an internal combustion engine system according to the inven- tion and upon which the method accord ing to the present invention is applicable,

Fig . 2 is a flow chart illustrating the steps carried out in a method according to an embodiment of the in- vention , and

Fig . 3 illustrates schematically an electron ic control unit according to the invention . DETAI LED DESCRI PTI ON OF AN EMBODI MENT OF TH E I NVENTION

Fig . 1 illustrates schematically an internal combustion engine system according to an embodiment of the present invention and upon which the method according to the invention is applicable. This system has a fuel feeding system with a main fuel tank 1 and a first pump 2 in the form of an electrical pump acting as a transfer pump pumping fuel from the main fuel tan k to a catch tan k 3. A second electrical pump 4 (may also be mechanical) is configured to pum p fuel from the catch tank further to a high-pressure part 5 of the fuel feeding system having a design being of no importance for the present invention besides containing injectors 6 for injecting fuel into cylinders 7 of an internal combustion engine 8. The combustion engine is arranged in a motor vehicle 9.

A level sensor 10 is arranged to indicate when the level of the fuel 1 1 inside the catch tank reaches a predetermined height which may be at a higher level than catch tank fuel levels during normal operation of the internal combustion engine system, but the level of fuel in the catch tan k may just as well under normal operation of the eng ine be higher than said predetermined level .

A control unit 12 is configured to obtain checking of the functionality of the first pump 2 by controlling the operation of the first pump 2 and the internal combustion engine 8 while receiving information from the level sensor 10 and a member 13 measuring the amount of fuel injected by the injectors 6 into the cylinders of the engine.

A method accord ing to an embodiment of the invention is carried out in the following way. The engine 8 is driven while carrying out the method which may be done during normal driving of the vehicle or offline in a workshop. The d ifferent steps of the method are controlled by the control un it 12, and the method is started by controlling the first pump 2 to operate in such a way that the level of the fuel 1 1 inside the catch tan k 3 aligns with the level sensor 10, which will then send information thereabout to the control unit controlling the first pump 2 to stop. The content of fuel in the catch tank is from the time of stopping the operation of the first pump indirectly measured by measuring the amount of fuel leaving the catch tank by ac- cumulating the amount of fuel injected in every injection of the injectors 6 from that moment and subtract th is amount from the content corresponding to the fuel level in alignment with the level sensor 10. When a predetermined start content of fuel in the catch tank is reached the first pump 2 is controlled to start and run at a fixed number of revolutions per minute. The time for said starting is recorded by the control unit as a starting time. The control unit does control the member 13 to start measuring the amount of fuel leaving the catch tan k as of said starting time by accumu lating the amount of fuel injected in every injection carried out by the injectors 6. The first pump 2 is controlled to operate so that the level of the fuel in the catch tank comes into alignment with the level sensor 10 again . The moment when this happens is recorded as a stop time and a duration of the first pump operation is by the control unit determined as the time elapse from said starting time to said stop time. The difference between the start content and the stop content is by the control unit determined as a first amount of fuel , and the control un it determines the amount of fuel injected by the injectors during said duration as a second amount of fuel . The control unit 12 is there- upon calculating the flow out of the first pump as (first amount of fuel + second amount of fuel) / duration and compare the value of this flow out calculated with the value of (displacement x number of revolutions per minute) / time, which is the flow out of the pump in an ideal case, to determining the functionality of the pump as the flow out calcu lated / ideal flow out, which may be called volumetric efficiency of the pump.

Fig . 2 illustrates a flow chart of a method accord ing to an embod iment of the present invention carried out for an internal combustion engine system of the type shown in Fig. 1 for checking the functionality of the first pump thereof. The method is started with a step S i of continu ing to drive the engine, which is done when carrying out all further steps of the method . The pump is then in a step S2 oper- ated to align the fuel level in the catch tan k with the level sensor. When the alignment has been obtained the operation of the pump is in a step S 3 stopped . I n a step S ₄ it is then started to calculate the accumulated amount injected by the injectors, i.e. estimated the amount of fuel leaving the catch tank. I n a step S 5 the question is asked if the accumu lated amount has reached a predetermined value mi , and when the answer to this question is yes the operation of the pump is started again while logging time ti in a step Se . A calculation of the accumulated amount injected by injectors is restarted at the time ti in a step S 7. In a step Ss the question is asked whether the catch tan k fuel level aligns with the level sensor, and when the answer to this question is yes the time is logged as and the pumping duration is calculated as the time it took the pump to fill the catch tan k back to the level sensor level . The accumulated amount injected by the injectors during t2-ti is determined as rri2. I n a step S10 the flow out of the pump is calculated as (mi +m2)/(t2-ti ) , whereu pon in a final step S n the volumetric efficiency of the pump is calculated as the flow out calculated / (displacement x number of revolutions per minute / 1) of the pump. Computer program code for implementing a method according to the invention is with advantage included in a computer program which can be read into the internal memory of a computer, e.g . the internal memory of an electron ic control unit of a motor vehicle. Such a computer program is with advantage provided via a com- puter program product comprising a data storage medium which can be read by a computer and which has the computer program stored on it. Said data storage medium is for example an optical data storage medium in the form of a CD ROM disc, a DVD d isc etc. , a magnetic data storage medium in the form of a hard disc, a diskette, a cassette tape etc. , or a flash memory or a memory of the ROM , PROM , EPROM or EEPROM type. Fig . 3 illustrates very schematically an electron ic control unit 12 comprising an execution means 14, e.g . a central processor unit (CPU), for execution of computer software. The execution means 14 communicates with a memory 15, e.g . of the RAM type, via a data bus 16. The control unit 12 comprises also a non-transitory data storage medium 1 7, e.g . in the form of a flash memory or a memory of the ROM , PROM , EPROM or EEPROM type. The execution means 14 commun icates with the data storage medium 1 7 via the data bus 16. A computer program comprising computer program code for implementing a method according to the invention , e.g . in accordance with the embodiment illustrated in Fig . 2, is stored on the data storage medium 1 7. The invention is of course in no way restricted to the embodiments described above, since many possibilities for modifications thereof are likely to be obvious to one skilled in the art without having to deviate from the scope of invention defined in the appended claims.