Fuel injection measurement and diagnostics

A control module comprising:

• a fuel injection module operating a fuel injector to provide fuel to a cylinder of an engine for a commanded energizing time based on a desired fuel amount;
• a pressure measurement module receiving pressure data for a predetermined crank angle window;
• a diagnostic module commanding the fuel injection module to keep the fuel injector off for a first cycle and receiving first pressure data from the pressure measurement module for the first cycle, commanding the fuel injection module to operate the fuel injector for a first energizing time during a second cycle and receiving second pressure data from the pressure measurement module for the second cycle, calculating a pressure ratio difference average (PRDA) from the first pressure data and second pressure data, and modifying the operation of the fuel injector based on the pressure ratio difference average.