Abstract: Fuel gelling determination methods and systems are provided for identifying and displaying to a vehicle operator a message conveying that the conditions are suitable for the formation of a fuel gel. In one particular example, at a fuel refill event the average ambient air temperature is calculated over the last fifty miles and used to characterize the grade of fuel as a summer or winter grade of fuel. Then, when the ambient temperature next drops near the cloud point of a summer fuel grade while driving, a message is displayed to a vehicle operator indicating that the conditions are suitable for fuel gelling to occur.

Abstract: Fuel gelling determination methods and systems are provided for identifying and displaying to a vehicle operator a message conveying that the conditions are suitable for the formation of a fuel gel. In one particular example, at a fuel refill event the average ambient air temperature is calculated over the last fifty miles and used to characterize the grade of fuel as a summer or winter grade of fuel. Then, when the ambient temperature next drops near the cloud point of a summer fuel grade while driving, a message is displayed to a vehicle operator indicating that the conditions are suitable for fuel gelling to occur.

Abstract: A method to protect a high-pressure fuel pump in a diesel-engine system includes enabling the high-pressure fuel pump when fuel pressure in the diesel-engine system is above a threshold, and disabling the high-pressure fuel pump if the fuel pressure is below the threshold. In this manner, the high-pressure fuel pump is protected from premature wear and failure due to inadequate lubrication.

Abstract: Onboard diagnostic monitors that are affected by a changing A/F activity resulting from fuel type mixture are disabled during such activity to avoid false malfunction diagnosis. A changing A/F is detected from the difference between a fast and a slow filtered value of an input signal from a fuel type sensor. If the difference value exceed a predetermined threshold, the monitors that are affected are disabled. After the A/F has stabilized, the filtered values converge and the monitoring is resumed.