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A flow regulating valve for a diesel engine in which a unitary valve element has three positions for controlling flow from a unit injector fuel injection system in response to valve inlet pressure. The valve has a first position wherein flow is blocked below about 10 psi, a second position between a

A flow regulating valve for a diesel engine in which a unitary valve element has three positions for controlling flow from a unit injector fuel injection system in response to valve inlet pressure. The valve has a first position wherein flow is blocked below about 10 psi, a second position between about 10 psi and 20 psi wherein flow is substantially unrestricted, and a third position above about 20 psi wherein flow is restricted to minimize return flow to a fuel supply and minimize fuel cooling requirements.

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The invention claimed is: 1. A fuel system for an internal combustion engine receiving a fuel supply for operating said engine with a series of timed, quantitatively selected fuel charges, said fuel system comprising: a fuel injection system for pressurizing fuel for delivery to the engine, a suppl

The invention claimed is: 1. A fuel system for an internal combustion engine receiving a fuel supply for operating said engine with a series of timed, quantitatively selected fuel charges, said fuel system comprising: a fuel injection system for pressurizing fuel for delivery to the engine, a supply and a return line extending between said fuel injection system and the fuel supply, at least one pump interposed in said supply line for receiving fuel from the fuel supply and delivering said flow to said fuel injection system, and a flow regulating valve interposed in the return line, said flow regulating valve comprising a housing having an inlet and outlet in a chamber interconnecting said inlet and outlet, and a valve element displaceable in said chamber between a first position wherein flow is blocked, a second position wherein flow is substantially unrestricted, and a third position where flow is restricted, said valve element being displaceable between said positions in response to the inlet pressure at said valve and said second position being between said first and third position. 2. A fuel system as claimed in claim 1, wherein the inlet pressure for the first position is lower than about 10 pounds per square inch (psi). 3. A fuel system as claimed in claim 1, wherein the inlet pressure for said second position is between about 10 and about 20 pounds per square inch (psi). 4. A fuel system as claimed in claim 1, wherein the inlet pressure for said third position is greater than about 20 pounds per square inch (psi). 5. A fuel system as claimed in claim 1, wherein said valve is yieldably urged to said first position against pressure at the inlet to said housing. 6. A fuel system as claimed in claim 5, further comprising a spring for yieldably urging said valve element toward said first position. 7. A fuel system as claimed in claim 1, wherein the flow area through said valve is a first level for the second position of said valve assembly and the flow area through said valve for the third position is smaller than the flow area in said second position. 8. A fuel system as claimed in claim 7, wherein the flow area in said second position is approximately eight times greater than the flow area for said third position. 9. A fuel system as claimed in claim 1, wherein said housing has a cylindrical chamber and has a valve seat, said valve element being displaceable against said valve seat blocking flow therethrough in said first position. 10. A fuel system as claimed in claim 9, wherein said valve element is biased towards said first position. 11. A fuel system as claimed in claim 10, further comprising a spring for biasing said valve element towards said first position. 12. A fuel system as claimed in claim 11, further comprising an O-ring on said valve element for abutting said valve seat in said first position. 13. A fuel system as claimed in claim 9, wherein said valve element has passages exposed to communicate the inlet of said housing to said outlet when said valve is away from said first position. 14. A fuel system as claimed in claim 13, wherein said valve element has a plurality of passages all of which permit flow to said outlet in said second position and permit flow to said outlet only through one of said passages when said valve element is in said third position. 15. A fuel system as claimed in claim 14, further comprising an annular outlet element positioned in said chamber between said valve element and the housing outlet, said outlet element having an end wall positioned to abut said valve element when said valve element is in said third position, said outlet element having a central recess open to said housing outlet and an axial central passage through said end face, said outlet element having a plurality of radial passages from the central recess to the outer circumference of said valve element, the passages in said valve element being positioned so that flow to the outlet of said housing is only through one of said passages and through said axial central passage of said outlet element. 16. A flow regulating valve for a fluid, said valve comprising: a housing having an inlet and outlet and a chamber interconnecting said inlet and outlets; a valve element displaceable in said chamber between a first position wherein flow is blocked, a second position wherein flow is substantially unrestricted; and a third position wherein flow is restricted, said valve element being displaceable between said first, second and third positions as a function of given pressure ranges and said second position being between said first position and said third position. 17. A flow regulating valve as claimed in claim 16, wherein the pressure for said first position is below about 10 pounds per square inch (psi), the pressure for said second position is between approximately 10 pounds per square inch and 20 pounds per square inch (psi) and the pressure for said third range is above approximately 20 pounds per square inch (psi). 18. A flow regulating valve as claimed in claim 16, wherein the flow area through said flow regulating valve has a first value for said second position and a second value for said third position, said third position being smaller than said second position. 19. A flow regulating valve as claimed in claim 18, wherein the flow area for said second position is approximately eight times greater than the flow area for said third position. 20. An engine system comprising: an internal combustion engine, a fuel supply, a fuel injection system for receiving fuel from said fuel supply and delivering a series of timed, quantitatively selected fuel charges to said engine under pressure, a supply and a return line extending between said fuel injection system and the fuel supply, at least one pump interposed in said supply line for receiving fuel from the fuel supply and delivering said flow to said fuel injection system, and a flow regulating valve interposed in the return line, said flow regulating valve comprising a housing having an inlet and outlet in a chamber interconnecting said inlet and outlet, and a valve element displaceable in said chamber between a first position wherein flow is blocked, a second position wherein flow is substantially unrestricted, and a third position where flow is restricted, said valve element being displaceable between said positions in response to the inlet pressure at said valve and said second position being between said first and third positions. 21. An engine system as claimed in claim 20 wherein said valve is interposed in said return line.