Fuel pump with inner channel priming

1. A pump unit for a fuel pump constructed and arranged to be disposed in a reservoir, the pump unit comprising:

a pump housing;

a pump cover;

a purge hole defined in the pump cover;

an impeller mounted for rotation between the pump housing and pump cover, wherein

the pump housing and pump cover having surfaces that cooperate to define a first channel and a second channel, each of the first and second channels having an inlet and an outlet,

the impeller having first vanes cooperating with the first channel and second vanes cooperating with the second channel, and

the outlet of the second channel being constructed and arranged to provide fuel to an engine upon rotation of the impeller,

a jet pump fluidly connected with the outlet of the first channel such that as the impeller rotates, fuel is delivered from the outlet of the first channel and through the jet pump causing fuel to be drawn into the reservoir; and

connecting structure fluidly connecting the first and second channels such that upon rotation of the impeller, fuel in the second channel flows into the first channel to prime the first channel.

2. The pump unit of claim 1 , wherein the pump cover has an inner channel and an outer channel and the pump housing has an inner channel and an outer channel, the inner channels cooperating to define the first channel and the outer channels cooperating to define the second channel.

3. The pump unit of claim 2 , wherein the connecting structure is a connecting channel fluidly connecting the inner and outer channels of the pump cover and a connecting channel fluidly connecting the inner and outer channels of the pump housing.

4. The pump unit of claim 3 , wherein the connecting channels are located at a position in the outer channels where the pressure is generally equal to a working pressure of the first channel, the working pressure of the first channel less than a system pressure to which the second channel builds.

5. The pump unit of claim 4 , wherein the working pressure is about 1 Bar and the system pressure is about 4 Bars.

6. The pump unit of claim 3 , wherein the connecting channels are sized and shaped to permit a flow rate of approximately 10 L/h there-through.

7. The pump unit of claim 2 , wherein the connecting structure is one of a connecting channel fluidly connecting the inner and outer channels of the pump cover or a connecting channel fluidly connecting the inner and outer channels of the pump housing.

8. The pump unit of claim 7 , wherein the connecting channel is in the pump cover and located downstream of the purge hole defined in the pump cover.

9. A pump unit for a fuel pump constructed and arranged to be disposed in a reservoir, the pump unit comprising:

a pump housing;

a pump cover defining a urge hole;

an impeller mounted for rotation between the pump housing and pump cover, wherein

the pump housing and pump cover having surfaces that cooperate to define a first channel and a second channel, each of the first and second channels having an inlet and an outlet,

the impeller having first vanes cooperating with the first channel and second vanes cooperating with the second channel, and

the outlet of the second channel being constructed and arranged to provide fuel to an engine upon rotation of the impeller,

means, fluidly connected with the outlet of the first channel, for drawing fuel into the reservoir upon rotation of the impeller; and

means for fluidly connecting the first and second channels such that upon rotation of the impeller, fuel in the second channel flows into the first channel to prime the first channel.

10. The pump unit of claim 9 , wherein the pump cover has an inner channel and an outer channel and the pump housing has an inner channel and an outer channel, the inner channels cooperating to define the first channel and the outer channels cooperating to define the second channel.

11. The pump unit of claim 10 , wherein the means for fluidly connecting the first and second channels is a connecting channel fluidly connecting the inner and outer channels of the pump cover and a connecting channel fluidly connecting the inner and outer channels of the pump housing.

12. The pump unit of claim 11 , wherein the connecting channels are located at a position in the outer channels where the pressure is generally equal to a working pressure of the first channel, the working pressure of the first channel less than a system pressure to which the second channel builds.

13. The pump unit of claim 12 , wherein the working pressure is about 1 Bar and the system pressure is about 4 Bars.

14. The pump unit of claim 11 , wherein the connecting channels are sized and shaped to permit a flow rate of approximately 10 L/h there-through.

15. The pump unit of claim 9 , wherein the means for drawing fuel is a jet pump.

16. The pump unit of claim 9 , wherein the connecting structure is one of a connecting channel fluidly connecting the inner and outer channels of the pump cover or a connecting channel fluidly connecting the inner and outer channels of the pump housing.

17. The pump unit of claim 16 , wherein the connecting channel is in the pump cover and located downstream of the purge hole defined in the pump cover.

18. A method of priming a jet pump of a fuel pump comprising:

providing a pump unit having a purge hole, an inner channel and an outer channel, and an impeller associated with the inner and outer channels to draw fuel into the inner and outer channel, the outer channel being constructed and arranged to provide fuel to an engine;

providing a jet pump fluidly connected with an outlet of the inner channel, the jet pump being constructed and arranged to cause fuel to be drawn into a reservoir associated with the fuel pump; and

priming the inner channel by permitting fuel in the outer channel to enter the inner channel.

19. The method of claim 18 , wherein the priming step includes fluidly connecting the inner and outer channels with a connecting channel.

20. The method of claim 18 , which includes locating the connecting channel at a position with respect to the outer channel where the pressure is generally equal to a working pressure of the inner channel, wherein the working pressure of the inner channel is less than a system pressure to which the outer channel builds.

21. The method of claim 20 , wherein the working pressure is about 1 Bar and the system pressure is about 4 Bars.