Method and system for supplying fuel to an engine

1. A method for fueling an engine, comprising:

receiving fuel data to a controller;

estimating fuel compressibility from the fuel data via instructions in the controller; and

adjusting output of a fuel pump via the controller in response to the estimated fuel compressibility, where adjusting output of the fuel pump includes increasing a voltage or an amount of current supplied to the fuel pump in response to the estimated fuel compressibility being greater than a threshold compressibility.

2. The method of claim 1 , where estimating fuel compressibility includes dividing a mass of fuel injected to the engine by a pressure drop in a fuel rail.

3. The method of claim 1 , where the fuel data includes fuel pressure in a fuel rail.

4. The method of claim 1 , where the fuel data includes an estimate of mass of fuel injected.

5. The method of claim 1 , further comprising adjusting output of the fuel pump via decreasing a voltage or an amount of current supplied to the fuel pump in response to the estimated fuel compressibility being less than a threshold compressibility.

6. A method for fueling an engine, comprising:

injecting fuel to an engine while a fuel pump that supplies fuel to the engine is stopped;

receiving fuel data to a controller while the fuel pump is stopped;

determining a change in fuel compressibility from a change in slope of pressure from the fuel data;

ensuring injection of liquid fuel to the engine via providing a desired fuel pressure, the desired fuel pressure a pressure above where the change in fuel compressibility occurs plus an offset pressure; and

adjusting output of the fuel pump via the controller in response to the desired fuel pressure.

7. The method of claim 6 , where the change in slope is indicative of at least a portion of fuel in a fuel rail being in a gaseous state.

8. The method of claim 7 , where the desired fuel pressure is greater than a fuel pressure where the slope changes, and where the desired fuel pressure is provided in a fuel rail.

9. The method of claim 6 , where the change in the slope is a decrease in slope.

10. The method of claim 6 , further comprising revising the desired fuel pressure in response to a change in fuel temperature or a refill of a fuel tank.

11. The method of claim 6 , where the fuel data received includes fuel pressure.

12. The method of claim 6 , where output of the fuel pump is adjusted to provide the desired fuel pressure.

13. The method of claim 6 , where injecting fuel to the engine while the fuel pump that supplies fuel to the engine is stopped is responsive to a change in fuel temperature or a fuel tank refill.

14. A system for controlling an engine, comprising:

an engine;

a fuel pump supplying fuel to the engine; and

a controller including executable instructions stored in non-transitory memory for adjusting output of the fuel pump responsive to compressibility of fuel supplied to the engine, where compressibility of fuel supplied to the engine is based on a mass of fuel injected divided by a change in fuel rail pressure.

15. The system of claim 14 , further comprising a fuel rail coupled to the engine and a fuel injector, and a pressure sensor coupled to the fuel rail.

16. The system of claim 15 , further comprising additional instructions to estimate the compressibility of fuel supplied to the engine based on output of the pressure sensor.

17. The system of claim 14 , further comprising additional instructions to determine a desired fuel pressure in response to the compressibility of fuel supplied to the engine.

18. The system of claim 17 , further comprising additional instructions for estimating the compressibility of fuel supplied to the engine responsive to a change in fuel temperature or a refill of a fuel tank.