초록 ▼

Methods and systems are provided for fuel systems including a gaseous fuel. Temporary flow restrictions in the fuel line of a first gaseous fuel may be addressed by temporarily shifting to cylinder operation with a second liquid fuel. Upon resumption of first fuel operation, if the flow restriction

Methods and systems are provided for fuel systems including a gaseous fuel. Temporary flow restrictions in the fuel line of a first gaseous fuel may be addressed by temporarily shifting to cylinder operation with a second liquid fuel. Upon resumption of first fuel operation, if the flow restriction persists, a diagnostic code may be set and cylinder operation with the second fuel may be restarted.

대표청구항 ▼

1. A method of operating an engine, comprising: responsive to a first fuel rail pressure below a rail threshold and a first fuel tank pressure of the first fuel above a tank threshold, alternating fuel injection to one or more engine cylinders from a first, gaseous fuel from a first fuel tank to a s

1. A method of operating an engine, comprising: responsive to a first fuel rail pressure below a rail threshold and a first fuel tank pressure of the first fuel above a tank threshold, alternating fuel injection to one or more engine cylinders from a first, gaseous fuel from a first fuel tank to a second, liquid fuel from a second fuel tank for a duration without refilling the first fuel tank, and then after the duration alternating back to the first fuel only if the first fuel rail pressure has risen above the rail threshold. 2. The method of claim 1, wherein the alternating fuel injection is further responsive to a second fuel rail pressure and a second fuel tank pressure of the second fuel. 3. The method of claim 1, wherein the alternating includes, injecting the first fuel until the first fuel rail pressure is below the rail threshold. 4. The method of claim 3, wherein the duration is responsive to ambient temperature, including a duration required to melt ice at a prevalent ambient temperature. 5. The method of claim 3, wherein injecting the second fuel includes, at least temporarily, automatically overriding a driver indicated preference for injection of the first fuel. 6. The method of claim 1, further comprising, in response to the first fuel rail pressure remaining below the threshold after the duration, injecting the second fuel. 7. The method of claim 6, further comprising, in response to the first fuel rail pressure being above the rail threshold after the duration, indicating a temporary flow restriction in a first fuel line via a first diagnostic code; andin response to the first fuel rail pressure being below the rail threshold after the duration, indicating a persistent flow restriction in the first fuel line via a second, different diagnostic code. 8. The method of claim 1, wherein the first fuel is a CNG fuel and the second fuel is a gasoline fuel. 9. A fuel system coupled to an engine, comprising: a first fuel tank configured to deliver a first gaseous fuel to an engine cylinder via a first fuel rail;a second fuel tank configured to deliver a second liquid fuel to the engine cylinder via a second fuel rail; anda control system with computer readable instructions for: while pressure in the first fuel tank is above a threshold pressure and while the first fuel tank is not refilled: temporarily increasing, for a duration, a proportion of the second fuel relative to the first fuel in a fuel injection to the engine cylinder responsive to a pressure of the first fuel rail being lower than a first threshold, the duration based on ambient temperature. 10. The fuel system of claim 9, wherein the proportion of the second fuel relative to the first fuel in the fuel injection is adjusted based on a pressure of the second fuel rail, the proportion being higher when the second fuel rail pressure is above a second threshold, and the proportion being lower when the second fuel rail pressure is below the second threshold. 11. The fuel system of claim 9, wherein the control system includes further instructions for, after the duration and if the first fuel rail pressure is above the first threshold, reducing the proportion of the second fuel relative to the first fuel; andafter the duration and if the first fuel rail pressure is below the first threshold, maintaining or further increasing the proportion of the second fuel relative to the first fuel. 12. The fuel system of claim 9, wherein the first fuel includes CNG and wherein the second fuel includes gasoline. 13. A fuel-injected engine method, comprising: while CNG tank pressure is above a tank threshold without being refilled: switching, for a duration based on ambient temperature, from injecting CNG to injecting liquid gasoline responsive to CNG rail pressure below a rail threshold; andswitching back to injecting CNG only if the CNG rail pressure has risen above the rail threshold; otherwise, maintaining injecting liquid gasoline. 14. The method of claim 13 further comprising setting a diagnostic code and limiting engine airflow in response to fuel rail pressure.