stumped on brake system for 93 ford van

i changed two front lines and master cylinder still no pressure. Back brakes grab. Bled system no air. what is wrong?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.