I am in the process of converting my Prusa I3 and Melzi controller to a RAMPS 1.4 system. Most things have gone well but the extruder stepper motor refuses to work. I have put the extruder motor on one of the directionnal controllers and it works fine. I have connected the X-axis stepper to the extruder pins and it does not work in that configuration. I have swapped the motor drivers with no success and I have switched the enable pin between normal and reversed without success. Any suggestions on what to try next?