Patent Publication Number: US-2017363054-A1

Title: Fuel injector assembly and method of use

Description:
BACKGROUND 
     The present invention relates to fuel injector assemblies, and in particular to a fuel injector assembly and methods of use particularly adapted to repair a damaged cylinder head in an internal combustion engine. 
     In a typical diesel engine, the fuel injectors are installed within cylinders in one or more cylinder heads. Each of the fuel injectors can be indirectly cooled by a coolant fluid circulated within the cylinder head by a cooling system. In some diesel engines, the cylinder walls between the fuel injectors and the coolant fluid path is relatively thin to enhance cooling. Unfortunately, the thin walls can be prone to cracking. Cracks in the cylinder walls can result in leakage of diesel fuel into the cooling system. In some engines, the factory installed injector cup, which fits within the cylinder and receives the fuel injector, can also crack, resulting in fuel leakage. 
     Standard methods for addressing a damaged cylinder include replacing the entire cylinder head in which the cylinder is located or attempting to cover up the crack with a sealing compound. Replacing the entire cylinder head is time consuming and costly, sometimes costing upwards of $4,000. Replacement costs may become in essence cost prohibitive as the age of the vehicle increases and the total value of the vehicle decreases. Sealing compounds applied directly to the cracked area often do not seal effectively and/or do not have sufficient duration to provide acceptable results. Repeatedly applying a sealing compound to a damaged cylinder can also become time consuming and cost prohibitive over time. 
     SUMMARY 
     The aforementioned issues are addressed by the present invention in which a fuel injector assembly including a replacement injector sleeve and a replacement injector lower body can be used to repair a damaged cylinder in a combustion engine in an efficient and cost effective manner. 
     The injector sleeve is used with a cylinder having an opening which receives a fuel injector, a bottom wall opposite the opening having a fuel injector bore formed therein for receiving a nozzle of the fuel injector, a cylinder sidewall connecting the opening and the bottom wall, and a fuel inlet passage formed in the cylinder sidewall. The replacement injector sleeve includes an injector sleeve body having an opening defined by an upper rim, the upper rim connected with a lower end of the injector sleeve body by an injector sleeve sidewall, the lower end defining an injector nozzle aperture, and the injector sleeve sidewall defining an injector sleeve fuel inlet. The injector sleeve body is configured to fit within the damaged cylinder such that the injector sleeve fuel inlet is at least partially aligned with the fuel inlet passage in the cylinder sidewall and the injector sleeve lower end abuts the cylinder bottom wall with the injector nozzle aperture at least partially aligned with the fuel injector bore. 
     According to another embodiment, fuel injector assembly is used in installing a fuel injector in a cylinder of a combustion engine, the cylinder having an opening which receives a fuel injector, a bottom wall opposite the opening having a fuel injector bore formed therein for receiving a nozzle of the fuel injector, a cylinder sidewall connecting the opening and the bottom wall, and a fuel inlet passage formed in the cylinder sidewall. The fuel injector assembly includes an injector sleeve that includes a injector sleeve body having an opening defined by an upper rim, the upper rim connected with a lower end of the injector sleeve body by an injector sleeve sidewall, an injector sleeve nozzle defined by the lower end of the injector sleeve body, and an injector sleeve fuel inlet defined by the injector sleeve sidewall. The fuel injector assembly also includes a fuel injector that includes an injector body including a nozzle for supplying fuel to a combustion chamber of the engine and a valve assembly for controlling a flow of fuel through the injector body to the nozzle, an electronic solenoid for controlling the valve assembly, and a lower body which receives the injector body and the nozzle, the lower body including at least one injector fuel inlet for supplying fuel to the nozzle through the injector body. When the injector sleeve and fuel injector are installed in the cylinder, (a) the injector sleeve fuel inlet is at least partially aligned with the at least one injector fuel inlet and the fuel inlet passage in the cylinder sidewall to supply fuel from the fuel inlet passage to the injector body, and (b) the lower end of the injector sleeve abuts the cylinder bottom wall with the injector sleeve nozzle aperture at least partially aligned with the fuel injector bore such that the nozzle passes through the injector sleeve to the fuel injector bore for supplying fuel to the engine combustion chamber. 
     In another embodiment, a method of repairing an engine in which fuel is leaking from a fuel injector cylinder into an adjacent coolant fluid passage, a fuel injector and injector sleeve within the cylinder, the cylinder having an opening which receives the fuel injector, a bottom wall opposite the opening having a fuel injector bore formed therein for receiving a nozzle of the fuel injector, a cylinder sidewall connecting the opening and the bottom wall, and a fuel inlet passage formed in the cylinder sidewall. The method includes removing the fuel injector and the injector sleeve from the cylinder, and installing a replacement injector sleeve in the cylinder. The replacement injector sleeve includes a sleeve body having an opening defined by an upper rim, the upper rim connected with a lower end of the sleeve body by a sleeve sidewall, the lower end of the sleeve body defining a nozzle aperture and the sleeve sidewall defining a sleeve fuel inlet, the installing step including aligning the sleeve fuel inlet with the fuel inlet passage formed in the cylinder sidewall. The method also includes aligning the sleeve fuel inlet with the fuel inlet passage formed in the cylinder sidewall and re-installing the fuel injector in the replacement injector sleeve installed in the cylinder, wherein the replacement injector sleeve inhibits fuel supplied through the fuel inlet passage from leaking into the adjacent coolant fluid passage. 
     Any of the above can further include the following or any combination thereof: (a) a distance between the upper rim and the lower end of the injector sleeve body is substantially similar to a distance between the opening and the bottom wall of the cylinder; (b) the injector sleeve body includes a first sealing portion adjacent the injector sleeve fuel inlet, a second sealing portion adjacent the lower end, and a cooling portion disposed between the first and second sealing portions and configured to be at least partially aligned with a cylinder coolant fluid passage when the injector sleeve body is installed in the cylinder; (c) the first and second sealing portions comprise a retaining compound for sealing with adjacent portions of the cylinder sidewall and bottom wall; (d) the injector sleeve is part of a kit that includes a replacement lower body for the fuel injector, the replacement lower body configured to fit within the injector sleeve body; (e) wherein a length of the injector sleeve sidewall is greater than a distance between the cylinder bottom wall and the fuel inlet passage; (f) further comprising replacing a lower body of the fuel injector with a replacement lower body prior to re-installing the fuel injector, the replacement lower body having a size and shape configured to be received within the replacement injector sleeve and at least one fuel inlet at least partially aligned with the sleeve fuel inlet; and (g) subsequent to installing the replacement injector sleeve, re-installing the fuel injector prior to allowing the retaining compound to finish curing. 
     These and other advantages and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a portion of a cylinder head of a combustion engine according to the prior art. 
         FIG. 2  is a perspective view of a fuel injector according to the prior art. 
         FIG. 3  is a side view of a fuel injection assembly according to an embodiment of the invention. 
         FIG. 4  is a perspective view of a replacement injector sleeve according to an embodiment if the invention. 
         FIG. 5  is a side view of a replacement injector sleeve according to an embodiment if the invention. 
         FIG. 6  is a side view of a replacement injector lower body according to an embodiment of the invention. 
         FIG. 7  is a perspective view of a replacement injector lower body according to an embodiment of the invention. 
         FIG. 8  is a side view of the replacement injector sleeve of  FIG. 5  installed in a prior art cylinder head of a combustion engine. 
         FIG. 9  is a flow chart demonstrating a process for installing a fuel injection assembly according to an embodiment of the invention. 
     
    
    
     DESCRIPTION 
     I. System 
       FIGS. 1 and 2  illustrate a portion of a combustion engine  10  and a fuel injector  12  according to the prior art. The combustion engine  10  includes a cylinder head  14  having one or more cylinders  16  configured to receive the fuel injector  12  for supplying fuel to an adjacent combustion chamber  18 . The cylinder head  14  also includes a coolant fluid passage  20  that is in fluid communication with a portion of the cylinder  16 . The coolant fluid passage  20  is typically filled with a circulating coolant fluid to cool the fuel injector  12  during use. 
     Still referring to  FIGS. 1 and 2 , the fuel injector  12  includes an injector upper body  30  housing a valve assembly (not shown) for controlling a flow of fuel through the injector upper body  30  to a nozzle  32  ( FIG. 2 ) which supplies the fuel to the combustion chamber  18 , as is known in the art. The injector upper body  30  is coupled with a lower body  34  which includes at least one injector fuel inlet  36 . Typically, the lower body  34  includes 2-3 fuel inlets spaced about the periphery of the lower body  34 . A pair of first and second gaskets  38  and  40 , illustrated in the form of O-rings, is provided on the lower body  34  above and below the injector fuel inlet  36 , respectively, to form a fluid tight seal around the injector fuel inlet  36 . The fuel injector  12  also includes an electronic solenoid  42  for controlling the valve assembly to control the flow of fuel through the fuel injector  12 . 
     The cylinder  16  is defined by an opening  50  in the cylinder head  14  that is connected with a bottom wall  52  by a cylinder sidewall  54 . The bottom wall  52  includes a fuel injector bore formed therein (not shown) through which the injector nozzle  32  supplies fuel to the combustion chamber  18 . A fuel inlet passage  56  is formed in an upper portion of the cylinder sidewall  54  for supplying fuel to the fuel injector  12  through the injector fuel inlet  36 . A coolant inlet  58  can be provided in a lower portion of the cylinder sidewall  54  to allow circulating coolant from the coolant fluid passage  20  to enter the cylinder  16 . The cylinder sidewall  54  also includes a first sealing groove  60  adjacent the opening  50  and a second sealing groove  62  below the fuel inlet passage  56  which together form a fluid tight seal with the first and second O-rings  38  and  40  on the fuel injector  12  to fluidly seal the fuel inlet passage  56  with the injector fuel inlet  36 . 
     Still referring to  FIG. 1 , the cylinder head  14  of the prior art includes an injector cup  66  received within the cylinder  16  below the fuel inlet passage  56 . The injector cup  66  includes a cup bottom wall  68  that abuts the cylinder bottom wall  52  which includes an opening that at least partially aligns with the fuel injector bore (not shown) in the cylinder bottom wall  52  through which the fuel injector nozzle  32  of  FIG. 2  extends. The injector cup  66  also includes a cup upper rim  70  that is connected to the cup bottom wall  68  by a cup sidewall  72 . A height of the cup sidewall  72  is configured such that the cup upper rim  70  is disposed above the coolant inlet  58  in the cylinder sidewall  54  to prevent coolant from entering the injector cup  66  and mixing with the fuel supplied by the injector nozzle  32 . The height of the cup sidewall  72  also prevents fuel supplied by the injector nozzle  32  from mixing with the coolant in the coolant fluid passage  20 . The interior dimensions of the cylinder  14  and the injector cup  66  together define an injector bore which is configured to receive a correspondingly shaped fuel injector  12 . 
     Referring now to  FIGS. 3-9 , a fuel injector assembly  100  according to an embodiment of the invention is illustrated for use in mounting a modified version of the fuel injector  12  within the cylinder  16  of the combustion engine  10 . The modification of the fuel injector  12  is described in more detail below and referred to as the modified fuel injector  120 . The fuel injector assembly  100  can be used to replace the prior art injector cup  66  to mount a fuel injector in the cylinder  16  in the event of damage to the cylinder sidewall  54 . In the prior art engine  10  of  FIG. 1 , damage to the cylinder sidewall  54 , particularly in the area between the injector cup  66  and the fuel inlet passage  56 , can result in an undesirable leaking of fuel from the cylinder  16  into the coolant fluid passage  20 , which can negatively impact engine performance. The fuel injector assembly  100  can be used to mount a fuel injector in the damaged cylinder  16  without the need to replace the entire cylinder head  14 . While the fuel injector assembly  100  is discussed in the context of replacing a prior art injector cup  66  in the event of damage to the cylinder sidewall  54  or bottom wall  52 , it will be understood that the embodiments described herein can be used to install a fuel injector in a cylinder at the time of assembly of the engine  10  or any other time, regardless of the status of the cylinder sidewall  54  and bottom wall  52 . 
     Referring now to  FIG. 3 , the fuel injector assembly  100  includes an injector sleeve  102  having a shape and dimensions configured to fit within the cylinder  16 . The injector sleeve  102  includes an injector sleeve body  104  having an opening defined by an upper rim  106  through which a modified fuel injector  120  is inserted. The injector sleeve  102  also includes a lower end  108  connected with the upper rim  106  by an injector sleeve sidewall  110 . As illustrated in  FIG. 3 , the injector sleeve  102  is configured such that when assembled within the cylinder  16 , the lower end  108  abuts the bottom wall  52  of the cylinder  16  and the upper rim  106  is disposed adjacent the cylinder opening  50 . Thus, a distance between the sleeve lower end  108  and the sleeve upper rim  106  can be based on a distance between the cylinder bottom wall  52  and the cylinder opening  50  such that the injector sleeve  102  substantially fills the cylinder  16 . 
     While the upper rim  106  of the injector sleeve  102  is illustrated as being aligned with the cylinder opening  50 , it will be understood that the injector sleeve sidewall  110  may be configured such that the upper rim  106  is disposed above or below the cylinder opening  50 . In one example, the injector sleeve sidewall  110  has a length such that the upper rim  106  is disposed at or above an upper edge of the fuel inlet passage  56  so as to provide a surface for forming a seal between the injector sleeve sidewall  110  and the cylinder sidewall  54  above the fuel inlet passage  56 . 
     The injector sleeve  102  can also include an injector sleeve fuel inlet  112  defined by the injector sleeve sidewall  110  such that the injector sleeve fuel inlet  112  is at least partially vertically aligned with the fuel inlet passage  56  when the injector sleeve  102  is assembled within the cylinder  16 . The dimensions and vertical position of the injector sleeve fuel inlet  112  can be selected so as to completely or partially align with the fuel inlet passage  56  in the cylinder  16  to allow fuel from the fuel inlet passage  56  to flow through the injector sleeve fuel inlet  112  to the modified fuel injector  120  when assembled. In one example, the injector sleeve fuel inlet  112  can have the same dimensions as the fuel inlet passage  56  and be formed in the sleeve sidewall  110  at a position in which the injector sleeve fuel inlet  112  and the fuel inlet passage  56  are completely aligned. In another example, the dimensions of the injector sleeve fuel inlet  112  and the vertical position of the injector sleeve fuel inlet  112  in the sleeve sidewall  110  can be selected so as to only partially align with the fuel inlet passage  56 . For example, a width and/or a height dimension of the injector sleeve fuel inlet  112  can be smaller or greater than the fuel inlet passage  56 . 
     Referring now to  FIGS. 4 and 5 , an injector nozzle aperture  114  is formed in the lower end  108  to allow the injector nozzle  32  of the fuel injector to pass through when assembled. The injector sleeve  102  has dimensions that generally correspond to an interior volume of the cylinder  16  to allow the injector sleeve  100  to be installed in the cylinder  16  and sealed with the sidewall  54  and the bottom wall  52 , as described in more detail below. As illustrated in  FIGS. 4 and 5 , the injector sleeve  102  can be provided with exterior surface features that generally mate with the interior features of the cylinder bottom wall  52  and sidewall  54  to facilitate securing and sealing the injector sleeve  102  within the cylinder  16 . 
     Referring now to  FIGS. 6 and 7 , the fuel injector assembly  100  also includes a replacement injector lower body  150  for use in supporting the fuel injector  12  within the injector sleeve  102 . When the injector sleeve  102  is being used to replace an originally installed injector cup  66 , the interior dimensions of the injector bore, as defined by the injector sleeve  102 , will be smaller and thus it is likely that the original lower body  34  will be too large to fit correctly within the injector sleeve  102 . The original lower body  34  can be removed according to the instructions provided with the fuel injector  12  and replaced with the replacement injector lower body  150  to form the modified fuel injector  120  for use with the injector sleeve  102 . Typically, the original lower body  34  is threadingly connected with the injector upper body  30  and thus can be removed using an appropriate tool. 
     Still referring to  FIGS. 6 and 7 , the replacement injector lower body  150  includes a body upper end  152  and a body lower end  154  connected by a body sidewall  156 . The body sidewall  156  includes at least one injector fuel inlet  158  spaced from the body lower end  154  a distance that is based on the position of the injector sleeve fuel inlet  112  in the injector sleeve sidewall  110 . In this manner, when the modified fuel injector  120  with the replacement injector lower body  150  installed thereon is installed into the injector sleeve  102 , the injector fuel inlets  158  are vertically aligned with the injector sleeve fuel inlet  112  to receive fuel supplied through the fuel inlet passage  58 . The body sidewall  156  also includes a sealing groove  160  for a seal, such as an O-ring (not shown), located between the injector fuel inlets  158  and the body upper end  152 . The body sidewall  156  can also include a series of flat faces  162  to facilitate gripping by a tool for threading the replacement injector lower body  150  onto the injector upper body  30 . A nozzle aperture  164  is provided in the body lower end  154 , through which the fuel injector nozzle  32  can pass. The dimensions of the injector sleeve  102  and the replacement injector lower body  150  can be configured such that the injector sleeve  102  encompasses the replacement injector lower body  150  from the body lower end  154  to at least beyond the sealing groove  160  such that the injector lower body  150  and the injector sleeve  102  can for a fluid tight seal above the injector fuel inlets  158 . 
     II. Method 
       FIG. 9  illustrates a cylinder repair process  200  using the fuel injector assembly  100  to address problems associated with a damaged cylinder. While the process  200  describes a method for installing the fuel injector assembly  100  in a damaged cylinder, it will be understood that a similar process can be used to install the fuel injector assembly  100  in a cylinder that is not damaged, either before or after market sale of the engine  10 . The cylinder repair process  200  is not limited to only those steps illustrated in  FIG. 9  and it will be understood that the process  200  can include fewer steps or additional steps and that the order of some of the steps may vary without deviating from the scope of the invention. The process  200  is described in the context of a 6.0 L diesel fuel engine, however the steps can be modified or skipped as needed based on the specifications of the engine being repaired. 
     The process  200  begins at  202  with identifying the damaged cylinder  16  which is causing leakage of fuel into the cooling system. Depending on the type of engine, this may include first determining which of multiple cylinder heads  14  is damaged before determining the specific cylinder  16  that is damaged. Typically the passenger side cylinder head will include the damaged cylinder and thus it is recommended to test the passenger side first. 
     One process for determining which cylinder head is damaged includes first disconnecting the fuel lines that run from each cylinder head to the secondary fuel filter on top of the engine and hold each of the fuel lines with the ends pointing upward to observe the level of fuel in each fuel line. Next, a cooling system pressure tester is installed and the pressure in the cooling system can be increased to around 30 Psi while observing the level of the fuel in each of the fuel lines. The level of fuel in the line connected to the damaged cylinder head will typically rise within the fuel line. 
     Once the damaged cylinder head  14  is identified, there are several exemplary methods which can be used to determine which cylinder  16  is damaged within that cylinder head  14 . One exemplary method includes visually identifying a crack in the cylinder sidewall  54 . To do this, each fuel injector  12  in the effected cylinder head  14  is removed, according to the manufacturer&#39;s instructions, and the sidewall  54  of each cylinder  16  is observed for cracks. In some cases, a small mirror may be helpful in investigating the cylinder sidewall  54 . The most common location for a cylinder crack is in the sidewall  54  opposite the cylinder fuel inlet passage  56 , such as the area  90  shown in  FIG. 1 . 
     If the damaged cylinder  16  cannot be identified visually, an optional process involving the cooling system can be used to attempt to identify which cylinder  16  is damaged. In this process, one or more fuel injectors  12  is removed from their respective cylinders  16  and the pressure in the cooling system can be increased using a cooling system pressure tester. The larger the leak, the more quickly coolant fluid will pass through the crack and into the cylinder  16 . In some instances, it may be beneficial to place a small piece of paper towel at the bottom of each cylinder  16  to facilitate visually identifying leakage of coolant fluid into the cylinder  16 . If this process for identifying a damaged cylinder  16  is used, it is recommended that any leaked coolant be removed from the cylinder  16  prior to re-assembly of the cylinder head  14  in order to avoid hydrolock following re-assembly. 
     Another optional process for identifying a damaged cylinder  16  includes visually looking for bubbles. This process may be particularly useful in cases in which the cracks are very small. First, the coolant fluid is drained from the cooling system to a level below the level of the cylinder heads  14 . The cooling system is then pressurized using a cooling system pressure tester. Once the system is pressurized, the interior of the cylinder sidewalls  54  can be soaked with soapy water. Cracks in the cylinder sidewalls  54  can be visually identified based on bubbles forming along the crack. 
     Another optional process, which may be used to identify extremely small leaks in the cylinder sidewall  54  that were not identifiable using any of the other previously described processes, includes plugging the injector nozzle opening in the cylinder bottom wall  52 . A 3/16ths vacuum cap can be pushed onto the end of a Phillips screwdriver and used to plug the injector nozzle opening. The cylinder  16  can then be filled with diesel fuel. A leak in the cylinder  16  can be identified by bubbles rising through the diesel fuel to the surface. 
     Once the damaged cylinder  16  is identified, at step  204  the factory installed injector cup  66  can be removed from the cylinder  16  using any suitable method, subsequent to removing the fuel injector  12 . In one example, a tap can be used to cut threads into an interior of the cup sidewall  72 . A threaded puller tool can then be coupled with the injector cup  66  through the cut threads and used to pull the injector cup  66  out of the cylinder  16 . 
     Once the factory installed injector cup  66  is removed, the replacement injector sleeve  102  can be installed in the cylinder  16  at step  206  (illustrated in  FIG. 8 ). Prior to inserting the replacement injector sleeve  102  into the cylinder  16 , at least a portion of the injector sleeve sidewall  110  and the injector sleeve bottom wall  108  is coated with a retaining compound. An exemplary retaining compound includes LOCTITE® 660, which is an acrylic-based anaerobic, adhesive metal retaining compound used in bonding cylindrical parts. 
     The retaining compound can be applied to the entire exterior surface of the injector sleeve sidewall  110  and sleeve bottom wall  108  or only a portion thereof. In one example, the retaining compound is applied to a first sealing portion including a portion of the injector sleeve sidewall  110  adjacent the injector sleeve fuel inlet  112  and the cylinder sidewall  54  and a second sealing portion that includes the sleeve bottom wall  108  and the adjacent sleeve sidewall  110  which come into contact with the cylinder sidewall  54  and bottom wall  52 . It is not necessary to apply the compound to the cooling portion of the injector sleeve sidewall  110  that is generally aligned with the coolant inlet  58 , and positioned between the first and second cooling portions. 
     The retaining compound can be applied to the replacement injector sleeve  102  and the replacement injector sleeve  102  can then be inserted into the cylinder  16  until the sleeve bottom wall  108  abuts the cylinder bottom wall  52 . It may be necessary to use a hammer and driver tool to insert the replacement sleeve  102  fully into the cylinder  16 . The replacement injector sleeve  102  should be installed such that the injector sleeve fuel inlet  112  is at least partially aligned with the fuel inlet passage  56 . The retaining compound can be applied and allowed to cure according to the manufacturer&#39;s instructions. Optionally, a retaining compound can be applied to the cylinder sidewall  54  and bottom wall  52  in addition to or as an alternative to applying the retaining compound to the injector sleeve  102 . 
     Prior to installing the replacement injector sleeve  102 , it is recommended to clean the cylinder  16  to facilitate binding of the retaining compound with the replacement injector sleeve  102  and the cylinder sidewall  54  and bottom wall  52 . Cleaning the cylinder  16  can include draining the coolant fluid to a level below the cylinder  16  to prevent any coolant fluid from affecting the retaining compound before it cures. Compressed air can optionally be used to blow back through the fuel line (which was previously disconnected at the fuel filter assembly) toward the cylinder head  14  so that fuel remaining in the fuel line or in the cylinder head  14  is purged, minimizing the chance that fuel will contaminate the sleeve retaining compound during curing. A hand vacuum pump or compressed air can also be used to remove any fuel or coolant fluid accumulated in the cylinder  16  to avoid a hydrolock condition. The cylinder  16  can optionally be cleaned used brake cleaning fluid and compressed air to decrease the chance that there is any remaining fuel or coolant fluid in the cylinder  16  that may affect the bonding of the retaining compound. 
     At step  208 , the injector lower body  34  can be replaced with the replacement injector lower body  150  so that the fuel injector  12  can be installed in the replacement injector sleeve  102 . To prepare the fuel injector  12 , the original tip gasket can be removed from the injector nozzle  32 . The fuel injector  12  can then be secured upside down (i.e. with the nozzle  32  pointing upward) in a suitable clamp or tool holder. The original injector lower body  34  can be unthreaded from the injector upper body  30  and carefully lifted off, preferably without disturbing any of the remaining stacked components within the fuel injector  12 . The replacement lower body  150  can then be threaded onto the upper body  30  and tightened thereon, thus forming the modified fuel injector  120 . 
     Prior to installing the replacement lower body  150 , the replacement lower body  150  and the exposed interior components of the fuel injector  12  can optionally be cleaned with brake cleaner and compressed air. The O-ring (not shown) that seals the upper body  30  with the lower body  34  can also be replaced at this time to provide a new O-ring for sealing the upper body  30  with the replacement lower body  150 . Clean engine oil can optionally be applied to the internal components of the fuel injector  12  prior to installing the replacement lower body  150 . Following the installation of the replacement lower body  150 , the fuel injector  12  can be cleaned using brake cleaner and compressed air. A new nozzle tip gasket can also be installed prior to installing the fuel injector  12 . 
     Because the replacement injector sleeve  102  substantially covers the replacement lower body  150 , the replacement lower body  150  only needs a single O-ring instead of the two O-rings  60  and  62  provided on the factory lower body  34  for use with the factory installed injector cup  66 . The single O-ring installed in the groove  160  in the replacement lower body  150  provides a seal between the injector sleeve sidewall  110  and the replacement lower body  150  above the injector fuel inlets  158  and the fuel inlet passage  58  in the cylinder  16  to inhibit fuel from leaking out of the top of the cylinder  16 . Unlike the factory lower body  34 , a second O-ring positioned below the injector fuel inlets  158  is not needed due to the presence of the replacement injector sleeve  102 . Some amount of accumulation of fuel at the bottom of the replacement injector sleeve  102  does not significantly impact engine performance. 
     Following installation of the replacement injector sleeve  102  and the replacement lower body  150 , the modified fuel injector  120  is installed in the replacement injector sleeve  102  at step  210 . Preferably, the modified fuel injector  120  is installed in the replacement injector sleeve  102  immediately following installation of the replacement injector sleeve  102  in the cylinder  16 . Installing the modified fuel injector  120  in the replacement injector sleeve  102  quickly, before the retaining compound completely cures, can minimize shifting of the replacement injector sleeve  102  as the retaining compound cures. The modified fuel injector  12  can be torqued according to the manufacturer&#39;s instructions and optionally torqued again after a predetermined period of time (e.g. 30 min.) to make sure the modified fuel injector  120  is seated properly within the replacement injector sleeve  102 . 
     Once the modified fuel injector  12  is installed in the replacement injector sleeve  102 , the remaining components of the engine  10  can be reassembled. It is generally recommended to wait at least a few hours before refilling the coolant fluid in the engine cooling system or turning the ignition on. The cooling system can optionally be flushed with a suitable detergent to remove fuel remaining in the system, although it is likely that some fuel will remain in the cooling system, which may decrease over time. 
     The replacement injector sleeve  102  and replacement lower body  150  can be sold together as a kit for repairing a damaged cylinder in a combustion engine. The kit may include additional components, such as the replacement lower body O-ring and other fuel injector related gaskets and the retaining compound. Some kits may optionally include tools used to remove the factory installed injector cup  66  and/or the driver tool used to install the replacement injector sleeve  102 . 
     III. Conclusion 
     The embodiments described herein provide a fuel injector assembly and method of use for addressing damaged engine cylinders without having to go through the labor intensive and costly process of replacing the cylinder head. The replacement injector sleeve described herein is configured to cover the cylinder sidewall and bottom wall to inhibit leakage of fuel from the fuel injector into the cooling system through the coolant inlet that surrounds a lower portion of the fuel injector. In this manner, fuel leakage into the cooling system can be inhibited even if existing cylinder cracks widen or new cracks form. 
     Alternative repair processes, such as replacing the entire cylinder head, are costly and time consuming. Attempts at using crack filling material in the cylinder often result in unsatisfactory results and do not protect against future crack widening or the formation of new cracks. The processes described herein using the fuel injector assembly with the replacement injector sleeve and replacement lower body provide a cost effective repair for a damaged cylinder that only requires a few hours of labor. 
     The above description is that of a current embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. 
     This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element of the described invention may be replaced by one or more alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. 
     The invention is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the above description or illustrated in the drawings. The invention may be implemented in various other embodiments and practiced or carried out in alternative ways not expressly disclosed herein. Also, the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the invention to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the invention any additional steps or components that might be combined with or into the enumerated steps or components. 
     The disclosed embodiment includes a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits. 
     Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular. 
     Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,” “upper,” “lower,” “inner,” “inwardly,” “outer” and “outwardly,” are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation.