Bad ABS pump?

My buddy's '96 has been sitting for over a year and brake fluid was leaking between the booster and master. I swapped in a spare dual diaphram booster and re-used the 2-output master that feeds the abs pump. The front brakes bleed fine, but no fluid comes out of the rear. I verified fluid coming out of the master rear line and into the abs pump rear input, but not coming out of the abs pump rear output(rear line disco'd). Today I took apart the abs pump and cleaned it out, but still no fluid passes through. Thoughts?