Water contamination sensing algorithms for ethanol containing fuel

A method for determining a level of water contamination in a fuel containing ethanol, comprising the steps of:

• determining an ethanol concentration of the fuel;
• sensing a resistance of the fuel;
• determining a resistance limit of the fuel using the ethanol concentration;
• and
• comparing the resistance to the resistance limit to provide the level of water contamination;
• and wherein the step of determining a resistance limit of the fuel using the ethanol concentration comprises the steps of:
• comparing the ethanol concentration to values on a look-up table, the look-up table including a plurality of ethanol concentrations and resistance values corresponding to the plurality of ethanol concentrations, wherein each resistance value represents a known resistance of fuel at a known level of water contamination;
• and
• multiplying a known resistance corresponding to the ethanol concentration by an alarm fraction to obtain the resistance limit.

A method for determining a level of water contamination in a fuel containing ethanol, comprising the steps of:

• determining an ethanol concentration of the fuel;
• sensing a resistance of the fuel;
• determining a resistance limit of the fuel using the ethanol concentration;
• wherein the step of determining a resistance limit of the fuel using the ethanol concentration comprises the step of comparing the ethanol concentration to values on a look-up table, the look-up table including a plurality of ethanol concentrations and resistance values corresoonding to the plurality of ethanol concentrations, wherein each resistance value represents a known resistance of fuel with no water contamination;
• and wherein a known resistance corresponding to the ethanol concentration is the resistance limit;
• and
• comparing the resistance to the resistance limit to provide the level of water contamination;
• wherein the step of comparing the resistance to the resistance limit to provide the level of water contamination comprises the steps of:
• calculating a normalized resistance by dividing the resistance by the resistance limit;
• and
• calculating a water contamination parameter, wherein the water contamination parameter=−1.6667*(normalized resistance)+1.6667.