High pressure oil limit based on fuel level to protect fuel injectors

1. An internal combustion engine comprising:

a control system;

a fuel system that draws liquid fuel from a fuel tank to charge fuel injectors that when actuated by the control system force fuel charges into engine combustion chambers using hydraulic fluid at injection control pressure (ICP); and

the control system comprising a processor for executing an ICP control strategy, wherein the strategy comprises processing a first fuel value indicative of the quantity of fuel presently in the tank and a second fuel value representing a quantity of fuel in the tank at which a maximum ICP limit set by the ICP control strategy should be changed, and when the result of the processing discloses that the second fuel value is less than the first fuel value, execution of the ICP control strategy reduces the maximum ICP limit from a greater value to a lesser value.

2. An engine as set forth in claim 1 wherein execution of the ICP control strategy conditions reduction of the maximum ICP limit from the greater value to the lesser value on the second fuel value being continuously less than the first fuel value for a defined length of time.

3. An engine as set forth in claim 1 wherein execution of the ICP control strategy restores the maximum ICP limit from the lesser value to the greater value when the result of the processing discloses that the second fuel value ceases to be less than the first fuel value.

4. An engine as set forth in claim 3 wherein execution of the ICP control strategy conditions restoration of the maximum ICP limit from the lesser value to the greater value on the second fuel value continuously ceasing to be less than the first fuel value for a defined length of time.

5. An engine as set forth in claim 1 comprising a switch function having inputs whose values correspond respectively to the greater and the lesser values of the maximum ICP limit, and wherein the switch function is controlled by the result of processing the first and second fuel values.

6. A fuel system and a control system for an internal combustion engine:

wherein the fuel system draws liquid fuel from a fuel tank to charge fuel injectors that when actuated by the control system force fuel charges into engine combustion chambers using hydraulic fluid at injection control pressure (ICP); and

wherein the control system comprises a processor for executing an ICP control strategy that comprises processing a first fuel value indicative of the quantity of fuel presently in the tank and a second fuel value representing a quantity of fuel in the tank at which a maximum ICP limit set by the ICP control strategy should be changed, and when the result of the processing discloses that the second fuel value is less than the first fuel value, causing the maximum ICP limit to be reduced from a greater value to a lesser value.

7. A fuel system and a control system as set forth in claim 6 wherein execution of the ICP control strategy conditions reduction of the maximum ICP limit from the greater value to the lesser value on the second fuel value being continuously less than the first fuel value for a defined length of time.

8. A fuel system and a control system as set forth in claim 6 wherein execution of the ICP control strategy restores the maximum ICP limit from the lesser value to the greater value when the result of the processing discloses that the second fuel value ceases to be less than the first fuel value.

9. A fuel system and a control system as set forth in claim 8 wherein execution of the ICP control strategy conditions restoration of the maximum ICP limit from the lesser value to the greater value on the second fuel value continuously ceasing to be less than the first fuel value for a defined length of time.

10. A fuel system and a control system as set forth in claim 6 comprising a switch function having inputs whose values correspond respectively to the greater and the lesser values of the maximum ICP limit, and wherein the switch function is controlled by the result of processing the first and second fuel values.

11. A method for control of injection control pressure (ICP) that is used to force the injection of fuel into an engine combustion chamber comprising:

processing a first fuel value indicative of the quantity of fuel presently in a fuel tank and a second fuel value representing a quantity of fuel in the tank at which a maximum ICP limit should be changed, and when the result of the processing discloses that the second fuel value is less than the first fuel value, causing the maximum ICP limit to be reduced from a greater value to a lesser value.

12. A method as set forth in claim 11 comprising conditioning reduction of the maximum ICP limit from the greater value to the lesser value on the second fuel value being continuously less than the first fuel value for a defined length of time.

13. A method as set forth in claim 11 comprising restoring the maximum ICP limit from the lesser value to the greater value when the result of the processing discloses that the second fuel value ceases to be less than the first fuel value.

14. A method as set forth in claim 13 comprising conditioning restoration of the maximum ICP limit from the lesser value to the greater value on the second fuel value continuously ceasing to be less than the first fuel value for a defined length of time.

15. A method as set forth in claim 11 comprising controlling a switch function by the result of processing the first and second fuel values to cause the switch function to pass one of the greater and the lesser values of the maximum ICP limit to the exclusion of the other based on the result of processing the first and second fuel values.