I have a 2001 Mitsubishi Montero xls not a sport

I have a 2001 mitsubishi montero xls not a sport. I replaced the brake relay switch and the accumulator because the anti lock buzzer and light is stuck on. After replacing these parts I thought his would fix my problem because once befor it did about 2 years ago. But it did not. So I tried to bleed the brakes to see if any air was in the lines. I could get fluid to the front lines but no through the back lines. I even tried to bleed at the master cylinder on the front lines would bleed but not the back. Is the a sing of a bad hydro pump?