Try advancing the pump a dime width before deciding to replace pump
OkTry advancing the pump a dime width before deciding to replace pump
OkTry advancing the pump a dime width before deciding to replace pump
I think this is a very likely cause.Something else, like a fuel crossover issue with the fuel selector valve and diesel overflowing from a tank, is about the only thing I can think of that fuel economy would look like 4 or 5 MPG.