A method for determining a state of health (SOH) value for a fuel delivery system in a vehicle includes estimating speeds of a calibrated fuel pump and an actual fuel pump using an extended state observer, calculating a deviation between the estimated speeds, and determining the progress of the deviation over a calibrated interval. The method further includes calculating the SOH value using the progress of the deviation, and automatically executing a control action corresponding to the SOH value. The system may be an Electronic Returnless Fuel System, and the pump may be controlled using pulse width modulation. A fuel delivery system for a vehicle includes a fuel pump operable for supplying fuel to the engine, a fuel tank containing the fuel pump, and a controller having the state observer noted above. A vehicle includes the fuel system, engine, and controller noted above.