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A dual fuel common rail fuel injector includes a first and second check needle used to selectively inject two different fuels such as diesel and liquefied natural gas. The fuel injector includes a fuel separator disposed in the interior cavity of the first check needle and is in sealing contact with

A dual fuel common rail fuel injector includes a first and second check needle used to selectively inject two different fuels such as diesel and liquefied natural gas. The fuel injector includes a fuel separator disposed in the interior cavity of the first check needle and is in sealing contact with the nozzle. The fuel separator is configured to prevent commingling of the diesel fuel and the liquefied natural gas. The fuel injector also includes at least one sealing member that is configured to prevent the diesel fuel from leaking from the diesel fuel check cavity into a gaseous fuel orifice.

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1. A dual fuel injector, comprising: an injector body configured to receive a first fuel and a second fuel;a nozzle having a first set of orifices for injecting the first fuel and a second set of orifices for injecting the second fuel;a first fuel check needle disposed in a first fuel check cavity,

1. A dual fuel injector, comprising: an injector body configured to receive a first fuel and a second fuel;a nozzle having a first set of orifices for injecting the first fuel and a second set of orifices for injecting the second fuel;a first fuel check needle disposed in a first fuel check cavity, and wherein the first fuel check needle defines an interior cavity;a second fuel check needle positioned within the interior cavity of the first fuel check needle and wherein the second fuel check needle is movable within a second fuel check cavity;a fuel separator having a first end and a second end, the fuel separator disposed in the interior cavity between the first fuel check needle and the second fuel check needle, the second end of the fuel separator disposed in sealing contact with the nozzle and configured to prevent commingling of the first fuel and the second fuel; andat least one sealing member configured to prevent the second fuel from leaking from the second fuel check cavity into the first set of orifices, the at least one sealing member contacting an internal surface of the first fuel check needle and a surface of the fuel separator, and the at least one sealing member is at least one of arranged between the fuel separator and a fuel separator biasing spring in contact with the fuel separator or arranged in a groove in the first fuel check needle. 2. The dual fuel injector of claim 1, further including a first biasing spring configured to bias the first fuel check needle toward a first position, and further includes a second biasing spring configured to bias the second fuel check needle toward a first position. 3. The dual fuel injector of claim 2, wherein the at least one sealing member is disposed in a constant line of contact around an exterior of the second fuel check needle at a junction between the first end of the fuel separator and a bottom end of the fuel separator biasing spring. 4. The dual fuel injector of claim 2, wherein the at least one sealing member is disposed between the fuel separator and the first fuel check needle and at a location between the first end of the fuel separator and the second end of the fuel separator. 5. The dual fuel injector of claim 2, wherein the at least one sealing member comprises: a first sealing member disposed in a constant line of contact around an exterior of the second fuel check needle at a junction between the first end of the fuel separator and a bottom end of the fuel separator biasing spring; anda second sealing member disposed between the fuel separator and the first fuel check needle and at a location between the first end of the fuel separator and the second end of the fuel separator. 6. The dual fuel injector of claim 1, wherein the injector body is configured to receive the first fuel and the second fuel delivered, via a quill, in a coaxial fashion. 7. The dual fuel injector of claim 2, wherein the second biasing spring is concentrically nested within the first biasing spring. 8. The dual fuel injector of claim 1, wherein the first fuel check needle is movable between a first position wherein the first fuel check needle blocks fluid communication with the first set of orifices, and a second position wherein the first fuel check needle at least partially allows fluid communication with the first set of orifices. 9. The dual fuel injector of claim 1, wherein the second fuel check needle is movable within the second fuel check cavity between a first position wherein the second fuel check needle blocks fluid communication with the second set of orifices, and a second position wherein the second fuel check needle at least partially allows fluid communication with the second set of orifices. 10. The dual fuel injector of claim 1, wherein the first fuel is a gaseous fuel and the second fuel is diesel fuel. 11. A dual fuel common rail fuel system comprising: a first fuel source;a second fuel source;a first fuel rail;a second fuel rail;at least one first fuel pump configured to pressurize a first fuel from the first fuel source and deliver the first fuel to the first fuel rail;at least one second fuel pump configured to pressurize a second fuel from the second fuel source and deliver the second fuel to the second fuel rail;a dual fuel injector fluidly coupled to the first fuel rail and to the second fuel rail, and further comprising:an injector body configured to receive the first fuel from the first fuel source and the second fuel from the second fuel source;a nozzle having a first set of orifices for injecting the first fuel and a second set of orifices for injecting the second fuel;a first fuel check needle disposed in a first fuel check cavity, and wherein the first fuel check needle defines an interior cavity;a second fuel check needle positioned within the interior cavity of the first fuel check needle and wherein the second fuel check needle is movable within a second fuel check cavity;a fuel separator having a first end and a second end, the fuel separator disposed in the interior cavity between the first fuel check needle and the second fuel check needle, the second end of the fuel separator disposed in sealing contact with the nozzle and configured to prevent commingling of the first fuel and the second fuel; andat least one sealing member configured to prevent the second fuel from leaking from the second fuel check cavity into the first set of orifices, the at least one sealing member contacting an internal surface of the first fuel check needle and a surface of the fuel separator, and the at least one sealing member is at least one of arranged between the fuel separator and a fuel separator biasing spring in contact with the fuel separator or arranged in a groove in the first fuel check needle. 12. The dual fuel common rail fuel system of claim 11, further including a first biasing spring configured to bias the first fuel check needle toward a first position, and further includes a second biasing spring configured to bias the second fuel check needle toward a first position. 13. The dual fuel common rail fuel system of claim 12, wherein the at least one sealing member is disposed in a constant line of contact around an exterior of the second fuel check needle at a junction between the first end of the fuel separator and a bottom end of the second biasing spring. 14. The dual fuel common rail fuel system of claim 12, wherein the at least one sealing member is disposed between the fuel separator and the first fuel check needle and at a location between the first end of the fuel separator and the second end of the fuel separator. 15. The dual fuel common rail fuel system of claim 12, wherein the at least one sealing member comprises: a first sealing member disposed in a constant line of contact around an exterior of the second fuel check needle at a junction between the first end of the fuel separator and a bottom end of the fuel separator biasing spring; anda second sealing member disposed between the fuel separator and the first fuel check needle and at a location between the first end of the fuel separator and the second end of the fuel separator. 16. The dual fuel common rail fuel system of claim 11, wherein the injector body is configured to receive the first fuel and the second fuel delivered, via a quill, in a coaxial fashion. 17. The dual fuel common rail fuel system of claim 12, wherein the second biasing spring is concentrically nested within the first biasing spring. 18. The dual fuel common rail fuel system of claim 11, wherein the first fuel check needle is movable between a first position wherein the first fuel check needle blocks fluid communication with the first set of orifices, and a second position wherein the first fuel check needle at least partially allows fluid communication with the first set of orifices. 19. The dual fuel common rail fuel system of claim 11, wherein the second fuel check needle is movable within the second fuel check cavity between a first position wherein the second fuel check needle blocks fluid communication with the second set of orifices, and a second position wherein the second fuel check needle at least partially allows fluid communication with the second set of orifices. 20. The dual fuel common rail fuel system of claim 11, wherein the first fuel is a gaseous fuel and the second fuel is diesel fuel.