Extruder Motor Problem

Hello,
I am having a problem where I am not able to manually tell my printer to extrude plastic. Through experimentation, I have found that the following components work fine:

Stepper Driver: Swapped X and E stepper drivers, X motor was able to use the E stepper driver with no problems.
Motor: Swapped X and E stepper plugs, E motor was able to move using the X pins.

Note that the hotend was above the minimum extrusion temp during all tests, and that each stepper driver was putting out plenty of power.

I am using a RAMPS 1.4 board running Marlin.

Does anybody have suggestions on what else might be going wrong?

Edited 1 time(s). Last edit at 06/25/2015 08:53PM by cadebot.

Also, the extruder moves freely when I turn it with my hand, not an issue of bonding and I am sure the motor is strong enough to drive it.

My problem was that the extruder steps per mm was set to 0 in Marlin.