AU2006201754A1

AU2006201754A1 - Method for Monitoring a Fuel Leak of an Injector for an LPI Vehicle

Info

Publication number: AU2006201754A1
Application number: AU2006201754A
Authority: AU
Inventors: Woo Jik Lee
Original assignee: Hyundai Motor Co
Current assignee: Hyundai Motor Co
Priority date: 2005-08-30
Filing date: 2006-04-27
Publication date: 2007-03-15
Anticipated expiration: 2026-04-27
Also published as: NL1031701A1; KR20070028639A; CN1924326A; ITMI20060838A1; AU2006201754B2; NL1031701C2; KR100716361B1; JP2007064206A; CN100441845C

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Actual Inventor: Address for Service: Invention Title: Details of Basic Application: Hyundai Motor Company Woo Jik Lee HODGKINSON McINNES PAPPAS Patent Trade Mark Attorneys Levels 3, 20 Alfred Street MILSONS POINT NSW 2061 "Method for Monitoring a Fuel Leak of an Injector for an LPI Vehicle" Korea Patent Application No. 10-2005-0080136 Filed 30 August 2005 The following statement is a full description of this invention, including the best method of performing it known to us: P20498AU00 METHOD FOR MONITORING A FUEL LEAK OF AN INJECTOR FOR AN LPI

VEHICLE

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0080136 filed in the Korean Intellectual Property Office on August 30, 2005, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for monitoring a fuel leak of an injector of an LPI vehicle. More particularly, the present invention relates to a method for monitoring a fuel leak of an injector of an LPI vehicle having advantages of reducing misfired hydrocarbon emissions and recognizing accurately a cause of an ignition problem.

Description of the Related Art In general, a liquefied petroleum gas injection (LPI) vehicle (or system), as shown in FIG. 1, is provided with a structure compressing liquefied petroleum gas (LPG) using a fuel pump 11 so as to maintain the LPG in a liquid state a state that 5 bar is added to the pressure in the bombe 10), and injecting the LPG through an injector 12.

If an ignition is turned off, interior fuel pressure of a fuel line which is positioned near to the injector 12 is gradually increased in respect to a predetermined pressure (bombe pressure 5bar) by the temperature of an engine compartment, and consequently the interior fuel pressure is increased up to an operation pressure (abut 10 bar) of an interior relief valve of the bombe At the same time, an interior fuel a gasified fuel) of the fuel line may leak through a tip of the injector 12 while the vehicle is parked. If such a leak occurs, since the fuel in a combustion chamber becomes very rich, ignition may become delayed and an emission amount of hydrocarbons (HC) may be increased.

If the temperature of the LPG is increased by radiant heat of the engine, since saturated vapor pressure is linearly increased, the interior fuel pressure of the fuel line is increased. In particular, if, after driving, the vehicle is parked for a long time, the interior fuel pressure of the fuel line may be more increased.

Accordingly, if the ignition of the engine is turned off, and if the interior fuel temperature and the interior fuel pressure of the fuel line, which is positioned near to the engine compartment, are increased, in order to return the interior fuel to the bombe 10, a structure is used in which a spring of a pressure controller is pushed by the increased interior fuel pressure.

As shown in FIG. 1, the injector 12 is mounted on the fuel line in the engine compartment, so as to inject the liquefied fuel. The injector 12 is also affected by interior fuel of high pressure, and accordingly, a fuel leak occurs through the tip between a needle and a sheet surface) of the injector. In addition, in a case that the injector 12 is used for a long time, the leakage amount of the interior fuel may be further increased due to abrasion of the tip and accumulation of carbon.

If such a fuel leak occurs, the fuel remains in an intake manifold or a combustion chamber, and accordingly, the starting performance is affected by the fuel when the ignition is next turned on. Under a state that the fuel leak occurs, if the ignition is turned on, since the amount of the fuel leak is added to an amount of fuel injected for a normal ignition, the fuel in the combustion chamber becomes rich. If the amount of the fuel leak is not significant, since the fuel of the combustion chamber is within a combustible range, a problem does not occur. However, if the amount of the fuel leak is excessive, since the fuel of the combustion chamber is out of the combustible range, a problem occurs that the ignition is delayed.

Furthermore, if the amount of the fuel leak is further increased, since the amount of the fuel leak may be out of the combustible range, a phenomenon occurs that an emission amount of misfired HCs is greatly increased.

According to the conventional method, in spite of a state that the amount of the fuel leak remains excessive in the combustion chamber, the fuel is still normally injected to the combustion chamber regardless of the fuel leak.

Accordingly, the emission amount of misfired HCs is further increased by the injected fuel, and consequently, problems occur that the emission amount may violate emission regulations and the ignition time may be long.

Prior art for solving such problems was published on July, 05, 2005 from the Korean Intellectual Property Office, as Korean Patent Application Number 10-2003-0100938 (refer to FIG. entitled "A method for controlling an ignition delay and a HC reduction of an LPI vehicle." The prior art has an advantage that the misfired HCs can be reduced without a reduction of the starting performance even if the fuel leak in the LPI engine occurs. Meanwhile, the fuel leak generally occurs in only one or two injectors of the vehicle. However, according to the prior art, if an error code is generated, all injectors in the vehicle if the vehicle has a six-cylindered engine, the number of injectors is 6) must be exchanged, and accordingly, a problem occurs that an exchanging cost is excessive.

In addition, if an LPG switch is turned off in an emergency, at a very low temperature ignition and by a problem of the fuel line, that is, if the ignition is delayed for a long time, a problem occurs that the ECU determines that a fuel leak occurs. In addition, although the cause of the ignition delay is solved by a reduction of the fuel leak, a problem occurs that the error code is generated.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method for monitoring a fuel leak of an injector of an LPI vehicle having advantages of reducing emission of misfired hydrocarbons and recognizing accurately a cause of an ignition problem.

A method for monitoring a fuel leak of an injector of a liquefied petroleum gas injection (LPI) vehicle according to an embodiment of the present invention, so as to control an ignition delay and to reduce hydrocarbon (HC) emission, includes: monitoring a lead time taken for ignition of an engine; determining whether the lead time is more than a target time; adding a number to a first count when the lead time is more than the target time, subtracting the number from the first count when the lead time is less than the target time and a hysteresis is satisfied, and storing the first count in an electronic control unit (ECU); comparing the added first count with a reference count; suppressing a fuel injection during a predetermined cycle when the added first count is more than the reference count, even though the ignition is turned on; and starting the fuel injection from the time that an engine rpm is reduced after a perfect explosion, if the perfect explosion is generated without fuel injection during the monitoring of the rpm of the engine under the suppressing of the fuel injection, and wherein the number is again added to the first count and the suppressing of the fuel injection is again performed, when the added first count is more than the reference count and when a coolant temperature is within a predetermined temperature.

The method according to the embodiment of the present invention further includes: determining whether a fuel leak error code is generated, when the added first count is more than the reference count; and suppressing the fuel injection when the fuel leak error code is not generated and when the coolant temperature is within the predetermined temperature.

The method according to the embodiment of the present invention further includes: determining whether a removal condition for removing the fuel leak error code is satisfied when the fuel leak error code is generated, the removal condition being satisfied when a warm-up cycle count (WUP_CYCCTR) is more than the reference count, the first count is less than an error reference count, and the added first count is reduced; and removing an error code and maintaining the added first count when the removal condition is satisfied.

In the method according to the embodiment of the present invention, the monitoring a lead time is performed when a presupposition condition is satisfied, the presupposition condition being satisfied when the ignition of the engine of the LPI vehicle is turned on, an error code is not generated in the ECU, a battery state is normal, a coolant temperature and a fuel temperature are within a predetermined temperature during all-night parking, an LPG switch is turned on, and the fuel temperature is more than a reference temperature the fuel temperature is not an extremely low temperature).

The method according to the embodiment of the present invention further includes: checking the added first count and determining whether the ignition is turned on when the presupposition condition is satisfied; determining whether the added first count is more than the reference count when the ignition is turned on; comparing the engine rpm with a perfect explosion determining rpm when the added first count is less than the reference count; and checking the lead time and determining whether the lead time is more than the target time, when the engine rpm is more than the perfect explosion determining rpm.

The method according to the embodiment of the present invention further includes: determining whether the hysteresis is satisfied when the lead time is less than the target time; and subtracting the number from the first count when the hysteresis is satisfied, and storing the subtracted first count in the

ECU.

The method according to the embodiment of the present invention further includes: performing a fuel leak reducing pattern, that is, a fuel injection suppressing pattern, when the added first count is more than the reference count in the step of determining whether the added first count is more than the reference count, and inputting the predetermined cycle for suppressing the injection to the ECU, the predetermined cycle being calculated on the basis of the added first count; comparing the engine rpm with the perfect explosion determining rpm; subtracting the number from the first count when the engine rpm is more than the perfect explosion determining rpm; determining whether a fuel leak error presupposition condition is satisfied, and inputting the subtracted first count to the ECU; and starting the fuel injection when the engine rpm is reduced.

The method according to the embodiment of the present invention further includes: determining whether the predetermined cycle for suppressing the fuel injection is complete, when the engine rpm is less than the perfect explosion determining rpm in the step of comparing the engine rpm; and starting normally the fuel injection after firing perfectly a leaked fuel by a learning control, which is learned such that one cycle is added to the predetermined cycle at the next ignition, if the perfect explosion of the engine is not generated when the predetermined cycle is complete.

The method according to the embodiment of the present invention further includes: determining whether an over-fuel leakage error determining condition is satisfied after starting the fuel injection; and storing the error code in the ECU, resetting the first count, and lighting a warning lamp such that the injector is exchanged due to an over-abrasion thereof, when the over-fuel leakage error determining condition is satisfied.

In the method according to the embodiment of the present invention, the over-fuel leakage error determining condition is satisfied when the first count is added and the fuel leak error presupposition condition is satisfied, and the fuel leak error presupposition condition is satisfied when the added first count (COUNT_SUM) and a non-injection ignition count (COUNT_SUMST) are more than the reference count.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a conventional system of an LPI vehicle.

FIG. 2 is a flowchart showing a conventional method for monitoring a fuel leak of an injector of an LPI vehicle.

FIG. 3 is a flowchart showing a method for monitoring a fuel leak of an injector of an LPI vehicle according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.

FIG. 3 is a flowchart showing a method for monitoring a fuel leak of an injector of an LPI vehicle according to an exemplary embodiment of the present invention. As shown in FIG. 3, a method for monitoring a fuel leak of an injector of an LPI vehicle according to the exemplary embodiment of the present invention includes adding the number to a first count whenever a lead time that is taken for an ignition of the engine is more than a target time, and suppressing a fuel injection with respect to the added first count. Accordingly, the present invention reduces emission of misfired hydrocarbons (HC) and recognizes accurately a cause of an ignition problem due to the fuel leak of the LPI engine.

In more detail, the lead time is monitored when an ignition of the LPI engine is turned on, the electronic control unit (ECU) determines whether the lead time is more than a target time that is stored therein, the number is added to the first count when the lead time is more than the target time, the number is conversely subtracted from the first count when the lead time is less than the target time and a hysteresis is satisfied, and the fuel injection is suppressed during a predetermined cycle when the added first count is more than the reference count, even though the ignition is turned on. At the same time, the predetermined cycle is calculated on the basis of the added first count.

In a case that a perfect explosion is generated by the leaked fuel without the fuel injection, conventionally the fuel injection starts from a time that starting of the engine is finished after the perfect explosion; about 700rpm).

However, although the perfect explosion is generated, leaked fuel may remain in the combustion chamber.

Under a state that the leaked fuel remains in the combustion chamber, if the fuel is normally injected after the perfect explosion is generated, misfired HCs may be increased.

Accordingly, it is preferable that the fuel injection starts from a time that the engine rpm is reduced through monitoring of the engine rpm. As a result, as above-mentioned, if the fuel is injected, since the leaked fuel is perfectly used, misfired HCs can be reduced compared with the conventional system.

Accordingly, it is preferable that a starting time of the fuel injection is not fixed, but can be varied. That is, the engine rpm is monitored and the fuel is injected from the time that the engine rpm is reduced after the perfect explosion, that is, the fuel is normally injected after the leaked fuel is perfectly burned, and as a result, misfired HCs can be reduced compared with the conventional system.

In more detail, at step S110, the ECU determines whether a presupposition condition is satisfied, the presupposition condition being satisfied when the ignition of the engine of the LPI vehicle is turned on, an error code is not generated in the ECU of the engine, a battery state is normal, a coolant temperature and a fuel temperature are within a predetermined temperature during all-night parking, an LPG switch is turned on, and the fuel temperature is more than the reference temperature, that is, the fuel temperature is not an extremely low temperature.

At step S110, if the presupposition condition is satisfied, the ECU, at step S120, checks the added first count and determines whether the ignition is turned on.

Here, the added first count is accumulated during a driving cycle, and the ECU memorizes the added first count. In addition if the engine rpm is more than a reference rpm, the ECU determines that the ignition is turned on.

At the step $120, if the ignition is turned on, the ECU, at step $130, determines whether the added first count is more than the reference count.

At the step S130, if the added first count (COUNT_SUM) is less than the reference count (COUNT_SUM _LEAK), the fuel is injected and is burned.

Thereafter, at step S240, the ECU compares the engine rpm with a perfect explosion determining rpm.

If the engine rpm is more than the perfect explosion determining rpm, the ECU, at step S150, checks the lead time (CYCNR_IGNITION) and determines whether the lead time is more than the target time.

Here, the lead time is calculated on the basis of the number of the driving cycle the number of the ignition), and in particular, the number of the driving cycle is counted from a time that the ignition is turned on to the time that the ignition is turned off. On the other hand, when the lead time is more than the target time means what the number of a starting necessary ignition cycle is equal to the number of predetermined ignition cycle or is more than that. Here, the number of the predetermined ignition cycle is a function of a fuel temperature.

At the step S150, if the lead time is more than the target time, the number is added to the first count as shown in the below formula, and the added first count is then stored in the ECU, at step S160.

Added first count: COUNTSUM(n) COUNTSUM(n-1) 1 At the step S150, if the lead time is less than the target time, the ECU determines whether a hysteresis is satisfied at step S170.

Here, if the number of the starting necessary ignition cycle is less than a value that a hysteresis value is subtracted from the number of the predetermined ignition cycle, the hysteresis is satisfied.

If the hysteresis is satisfied, the number is subtracted from the first count as shown in the below formula, and the subtracted first count is, at step S160, stored in the ECU.

Subtracted first count: COUNT_SUM(n) COUNT_SUM(n-1) -1 At the step 3130, if the added first count is more than the reference count, the ECU preliminarily determines that a fuel leak of the injector is excessive. At step S132, the ECU determines whether a fuel leak error code is generated.

If the fuel leak error code is not generated, the ECU, at step S138, determines whether a temperature condition is firstly satisfied, so as to determine whether a fuel leak reducing pattern is performed.

That is, the ECU determines whether a coolant temperature satisfies a temperature condition is a room temperature) at the ignition, is not an extremely low temperature or high temperature. If the coolant temperature satisfies the temperature condition is a room temperature), the fuel leak reducing pattern is performed at step S180, and if not, the fuel is directly injected at step 3210.

At the step S132, if the fuel leak error code is generated, at step 3134, the ECU determines whether a removal condition for removing the fuel leak error code is satisfied, the removal condition being satisfied when a warm-up cycle count (WUP_CYCCTR) is more than the reference count (WUPCYC_CTR reference count), the first count is less than an error reference count (COUNT_SUM error reference countOFF), and the added first count is reduced (COUNTSUM(n) COUNT_SUMST(n)).

If the removal condition is satisfied, the ECU, at step S136, removes an error code, and maintains the added first count and a non-injection ignition count as shown in the below formula.

Added first count maintenance; COUNT_SUM COUNT_SUM(n) Non-injection ignition count maintenance; COUNT_SUMST COUNT_SUMST(n) At the step S134, if the removal condition is not satisfied, the ECU, at the step S138, determines whether the fuel leak reducing pattern is performed.

As above-mentioned, if the coolant temperature satisfies the temperature condition, the ECU, at step S180, performs the fuel leak reducing pattern of the LPI vehicle, that is, the fuel injection suppressing pattern. At the same time, the predetermined cycle for suppressing the fuel injection is calculated on the basis of the added first count, and is stored in the ECU.

Thereafter, the ECU compares the engine rpm with the perfect explosion determining rpm, at step S190.

If the engine rpm is more than the perfect explosion determining rpm, the ECU, at step S200, determines whether the fuel leak in the injector occurs.

Thereafter, as shown in the below formula, the number is added to the non-injection ignition count (COUNTSUMST), and the added non-injection ignition count is stored in the ECU.

Added non-injection ignition count: COUNT_SUMST(n) COUNTSUMST(n-1)+1 (Here, the initial value of COUNT_SUMST= 0) In addition, at the step S200, the ECU subtracts the number from the first count, calculates an average value of the engine rpm, and determines whether the engine rpm is reduced.

Abstracted first count; COUNT_SUM(n) COUNT_SUM(n-1) 1 If the engine rpm is reduced, the ECU starts the fuel injection at step S210.

In addition, an amount of fuel injection is calculated by the formula "pressure compensation valuexbasic fuel amount of each driving condition." On the other hand, at the step S190, if the engine rpm is less than the perfect explosion determining rpm, the ECU, at step S240, determines whether the predetermined cycle for suppressing the fuel injection is complete.

If the perfect explosion of the engine is not generated when the predetermined cycle is complete, the ECU starts normally the fuel injection, after burning perfectly the leaked fuel, by a learning control, which is learned such that cycle is, as shown in the below formula, added to the predetermined cycle number at the next ignition.

Added predetermined cycle; COUNT_SUM(n) COUNT_SUM(n-1) +1 At the step S240, if the predetermined cycle is not complete, the ECU performs the fuel leak reducing pattern at the step S180.

At the step S210, after the fuel is injected, the ECU, at step S220, determines whether the over-fuel leakage error determining condition is satisfied, and the over-fuel leakage error determining condition is satisfied when the first count is added (COUNT_ SUM(n) COUNT_SUM(n-1)) and the fuel leak error presupposition condition is satisfied, and the fuel leak error presupposition condition is satisfied when the added first count (COUNTSUM) and a non-injection ignition count (COUNT_SUM_ST) are more than the reference count (COUNT_SUMST(n) reference count_ON and COUNT_SUM error reference count_ON).

If the over-fuel leakage error determining condition is satisfied, at step S230, the ECU stores the error code, resets the first count, and lights a warning lamp such that the injector is exchanged due to an over-abrasion thereof.

First count; COUNT_SUM COUNT_SUMLEAK (Reference count) Non-injection ignition count; COUNT_SUM_ST(n) 0 For the warm-up cycle count, one cycle is from a time that the ignition is turned on under a cold state to a time that the ignition is turned off under a warm-up state (a state that the coolant temperature is more than the predetermined temperature).

As above-mentioned, the lead time is monitored when an ignition of the LPI engine is turned on, and the ECU determines whether the lead time is more than the target time that is stored therein.

In addition, during performing the fuel leak reducing pattern, that is, during performing the fuel injection suppressing pattern, at step S180, the lead time is calculated on the basis of the number of the driving cycle the number of the ignition). In addition, the target time is a function of the coolant temperature.

If the lead time is more than the target time, the number is added to the first count for determining an ignition delay, while on the contrary, the number is subtracted from the first count when the lead time is less than the target time and a hysteresis is satisfied. Here, the hysteresis is satisfied when the number of the starting necessary ignition cycle is within a value which hysteresis value is subtracted from the number of the predetermined ignition.

If the added first count is more than the reference count, the fuel injection is suppressed during a predetermined cycle, even though the ignition is turned on. Accordingly, in a case that the ignition time is occasionally long, a logic for suppressing the fuel injection of the present invention is not performed.

In addition, the logic must be applied only in a case that the LPI vehicle is in an all-night parking state since the phenomenon of the fuel leak occurs over a long time.

In addition, since the ignition time is affected by the battery state and an initial engine temperature, it is preferable that a minimum reference value thereof is also considered.

In addition, a starting condition is satisfied when an engine rpm condition starting determining rpm: more than 100rpm) and a line fuel pressure condition (more than a predetermined pressure when the ignition is turned on) are satisfied.

In addition, if the fuel injection is continuously suppressed under an over-fuel leakage state, the leaked fuel is gradually reduced by an engine operation, and, at the same time, an intake air is gradually increased.

Consequently, since the leaked fuel and the air may become appropriately mixed with each other, the mixed gas is burned by the ignition without fuel injection.

The predetermined cycle for suppressing the fuel injection is calculated on the basis of the first count for determining the ignition delay, the ECU determines whether the perfect explosion a state that the engine rpm reaches an ignition determining rpm) is generated and if the perfect explosion is generated without fuel injection, the number is subtracted from the first count, and cycle is subtracted from the predetermined cycle number after all-night parking.

On the contrary, the leaked fuel is perfectly burned by the learning control, which is learned such that cycle is added to the predetermined cycle number at the next ignition, and thereafter, the fuel is injected.

In a case that the perfect explosion is generated by the leaked fuel without fuel injection, conventionally the fuel injection starts from a time that a starting of the engine is finished after the perfect explosion; or about 600 to 800 rpm under room temperature). However, although the perfect explosion is generated, leaked fuel may remain in the combustion chamber.

Under a state that the leaked fuel remains in the combustion chamber, if the fuel is normally injected after the perfect explosion (about 700 rpm) is generated, misfired HCs may be increased.

Accordingly, it is preferable that a starting time of the fuel injection is not fixed, but can be varied. That is, as above-mentioned, the engine rpm is monitored, the fuel is injected from a time that the engine rpm is reduced after the perfect explosion, that is, the fuel is normally injected after the leaked fuel is perfectly burned, and as a result, misfired HCs can be reduced compared with the conventional system.

On the other hand, when the predetermined cycle is increased but the starting time is not reduced, the ECU determines that the abrasion of the injector is excessive, and so the ECU lights a warning lamp such that the injector is exchanged due to an over-abrasion thereof. Consequently, the present invention can solve the problems, such as with a starting performance and an emission gas, due to a fuel leak of the injector.

As has been explained, the method for monitoring a fuel leak of an injector for a liquefied petroleum gas injection (LPI) vehicle according to an exemplary embodiment of the present invention may have the following advantages. According to the embodiment of the present invention, misfired hydrocarbons can be reduced, a cause of an ignition problem can be accurately recognized, and a starting performance can be improved.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

The term "comprising" (and its grammatical variations) as used herein is used in the inclusive sense of "having" or "including" and not in the exclusive sense of "consisting only of".

Claims

1. A method for monitoring a fuel leak of an injector of a liquefied petroleum gas injection (LPI) vehicle so as to control an ignition delay and to reduce hydrocarbon (HC) emission, the method comprising: monitoring a lead time taken for an ignition of an engine; determining whether the lead time is more than a target time; adding a number to a first count when the lead time is more than the target time, subtracting the number from the first count when the lead time is less than the target time and a hysteresis is satisfied, and storing the first count in an electronic control unit (ECU); comparing the added first count with a reference count; suppressing a fuel injection during a predetermined cycle when the added first count is more than the reference count, even though the ignition is turned on; and starting the fuel injection from a time that an engine rpm is reduced after a perfect explosion, if the perfect explosion is generated without the fuel injection during the monitoring of the rpm of the engine under the suppressing of the fuel injection, and wherein the number is again added to the first count and the suppressing of the fuel injection is again performed, when the added first count is more than the reference count and when a coolant temperature is within a predetermined temperature.

2. The method of claim 1, further comprising: determining whether a fuel leak error code is generated, when the added first count is more than the reference count; and suppressing the fuel injection when the fuel leak error code is not generated and when the coolant temperature is within the predetermined temperature.

3. The method of claim 2, further comprising: determining whether a removal condition for removing the fuel leak error code is satisfied when the fuel leak occurs, the removal condition being satisfied when a warm-up cycle count (WUP_CYC_CTR) is more than the reference count, the first count is less than an error reference count, and the added first count is reduced; and removing an error code and maintaining the added first count when the removal condition is satisfied.

4. The method of claim 3, wherein the monitoring of the lead time is performed when a presupposition condition is satisfied, the presupposition condition being satisfied when the ignition of the engine of the LPI vehicle is turned on, an error code is not generated in the ECU, a battery state is normal, a coolant temperature and a fuel temperature are within a predetermined temperature during an all-night parking, an LPG switch is turned on, and the fuel temperature is more than the reference temperature the fuel temperature is not an extremely low temperature). The method of claim 4, further comprising: checking the added first count and determining whether the ignition is turned on when the presupposition condition is satisfied; determining whether the added first count is more than the reference count when the ignition is turned on; comparing the engine rpm with a perfect explosion determining rpm when the added first count is less than the reference count; and checking the lead time and determining whether the lead time is more than the target time, when the engine rpm is more than the perfect explosion determining rpm.

6. The method of claim 5, further comprising: determining whether the hysteresis is satisfied when the lead time is less than the target time; and subtracting the number from the first count when the hysteresis is satisfied, and storing the subtracted first count in the ECU.

7. The method of claim 5, further comprising: performing the fuel leak reducing pattern, that is, the fuel injection suppressing pattern, when the added first count is more than the reference count in the step of determining whether the added first count is more than the reference count, and inputting the predetermined cycle for suppressing the injection to the ECU, the predetermined cycle being calculated on the basis of Sthe added first count; Scomparing the engine rpm with the perfect explosion determining rpm; subtracting the number from the first count when the engine rpm is more than the perfect explosion determining rpm, determining whether a fuel leak S 5 error presupposition condition is satisfied, and inputting the subtracted first count 0 to the ECU; and (N Istarting the fuel injection when the engine rpm is reduced.

8. The method of claim 7, further comprising: determining whether the predetermined cycle for suppressing the fuel injection is complete, when the engine rpm is less than the perfect explosion determining rpm in the step of comparing the engine rpm; and starting normally the fuel injection after firing perfectly a leaked fuel by a learning control, which is learned such that one cycle is added to the predetermined cycle at the next ignition, if the perfect explosion of the engine is not generated when the predetermined cycle is complete.

9. The method of claim 8, further comprising: determining whether an over-fuel leakage error determining condition is satisfied after starting the fuel injection; and storing the error code in the ECU, resetting the first count, and lighting a warning lamp such that the injector is exchanged due to an over-abrasion thereof, when the over-fuel leakage error determining condition is satisfied. The method of claim 9, wherein: the over-fuel leakage error determining condition is satisfied when the first count is added and the fuel leak error presupposition condition is satisfied; and the fuel leak error presupposition condition is satisfied when the added first count (COUNT_SUM) and a non-injection ignition count (COUNT_SUM_ST) are more than the reference count.

11. A method for monitoring a fuel leak of a LPI vehicle so as to control an ignition delay and to reduce hydrocarbon emission as substantially hereinbefore described and with reference to Figure 3. Dated this 2 7 th day of April 2006. Hyundai Motor Company By: HODGKINSON MclNNES PAPPAS Patent Attorneys for the Applicant