Claims:We Claim:
1. A fuel injection system 100, comprising at least a fuel tank 103, a metering unit 102 downstream of said fuel tank 103, at least one end of said metering unit 102 opening into an inlet of a high pressure fuel injection pump 104, said high pressure fuel injection pump 104 in flow communication with an injector 106; characterized in that:

a single plunger feed pump 108 mechanically linked to an engine and located downstream of said fuel tank 103 and upstream to said metering unit 102, such that delivery of fuel from said single plunger feed pump 108 corresponds to a suction stroke of said high pressure fuel injection pump 104.

2. The fuel injection system 100 of claim 1, said single plunger feed pump 108 and said high pressure fuel injection pump 104 are mounted on a cam shaft, said cam shaft adapted to receive drive from said engine.
, Description:Field of the invention
[0001]This invention relates to the field of fuel injection system.

Background of the invention
[0002] In a fuel injection system, fuel from the fuel tank is delivered to the high pressure fuel injection pump with the help of an electric feed pump. For low cost solution and for emerging market, the use of the electric feed pump is expensive. There is a need to pump the fuel from the fuel tank to the high pressure fuel injection pump in cases where the use of electric feed pump is not possible or expensive.

Brief description of the accompanying drawing
[0003] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0004] FIG. 1 illustrates a fuel injection system; and

[0005]FIG. 2 illustrates a graph showing the cam positions of the single plunger feed pump and the fuel injection pump.

Detailed description of the embodiments
[0006] FIG. 1 illustrates a fuel injection system 100. The fuel injection system 100 comprises at least a fuel tank 103, a metering unit 102 downstream to the fuel tank 103, at least one end of said metering unit 102 opening into an inlet of a high pressure fuel injection pump 104, the high pressure fuel injection pump 104 in flow communication with an injector 106. A single plunger feed pump is mechanically linked to an engine and located downstream of the fuel tank 103 and upstream to the metering unit 102, such that delivery of fuel from the single plunger feed pump corresponds to a suction stroke of the high pressure fuel injection pump 104. The single plunger feed pump and the high pressure fuel injection pump 104 are mounted on a cam shaft.

[0007]The working of the fuel injection system 100 will be explained in further detail. The fuel injection system 100 comprises a fuel tank 103 that is used to store fuel. Fuel from the fuel tank 103 flows to a single plunger feed pump (?) that is mechanically linked to an engine. The single plunger feed pump is located downstream of the fuel tank 103 and upstream to the metering unit 102. The single plunger feed pump is driven by a cam. The cam receives motion from the engine crankshaft. The profile of the cam is such that the delivery stroke of fuel from the single plunger pump 108 corresponds to the suction stroke for the high pressure fuel injection pump 104, herein referred to as the main pump. In other words profile of the cam that is used to drive the single plunger feed pump matches with the profile of the cam that drives the main pump. Consider the example of a suction stroke in the main pump. The fuel injection pump 104 comprises a piston, during suction stroke the piston creates a volume for fuel to be sucked into cylinder of the main pump. The piston 107 that is located in the plunger pump compresses the fuel causing the fuel to flow from the plunger pump to the main pump. Once the fuel that is delivered from the main pump to the injector 106, the position of the piston in the main pump will be at the top dead centre. The single plunger pump 108 will suck additional fuel from the fuel tank 103 in order to ensure that sufficient fuel is available in the main pump during the next suction stroke of the main pump.

[0008]FIG. 2 illustrates a graph showing the cam positions of the single plunger feed pump 108 and the high pressure fuel injection pump 104. Y1 represents cam position of the single plunger feed pump, while Y2 represents cam position of the fuel injection pump. Points 1 the position of the piston of the single plunger feed pump 108 when it is at the top dead centre, and point 2 represents the position of the piston of the fuel injection pump when it is at the bottom dead centre. From FIG. 2, it is clear that the compression stroke of the single plunger feed pump 108 happens during the suction stroke of the high pressure fuel injection pump 104.

[0009]It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.