Proportioning valve issues.

[83swb]

Just redid the WHOLE brake system on my truck, with the exception of a booster.

I bought a CPP factory style combination valve to replace the factory one that was in rough shape. All the brakes are plumbed correctly and the master cylinder and booster are in working order. I'm only getting some fluid to the rear brakes and the drivers side front caliper, the passenger side caliper is bone dry. I have a little pedal with the truck not running and no pedal when the truck is running (after some bleeding obviously).

I know there's some crazy sliding valve in the combination block, but how do I get it to open up?