Okay, so I have a (new to me) 93 pickup. When I bought it the brakes were spongey so I knew they needed work. Found a leak in the lines near the fuel tank, so we dropped the tank replaced both lines that run along that side and to the LSPV. Once we tried to bleed we couldn’t get any pressure to build back up and the pedal went to the floor so i immediately thought master cylinder.
New master and bench bled it. When we went to reattach it and swap bleeder plugs to brake lines we struggled to get the shorter one back on as we tightened the master cylinder too tight, which took us about 5- 10 ish mins to realign and reattach. Then we went to bleed everything again and we were struggling to get enough fluid to come out and still no brakes. Repeating the bleeding process a few times enough fluid comes out the back drums but not the front callipers… but still no pressure building in pedal. I haven’t tried to bleed the proportioning valve but I read to bleed it after all 4 brakes, it looks rusty.
Otherwise I’m stumped to why there’s not much fluid coming out and we can’t build pressure. Did a lot of air get it while swapper bleeder plugs to lines? Faulty master or piston in it? Any tips would be great!

 

if the back slaves are bleeding clean with no air bubbles i'd work on the fronts, not the lspv, try letting them drip-bleed for awhile.

it's possible that the master got air in it, i've "bench bled" the master by myself while it was in the truck by pumping the pedal and cracking the brake line connector, using a 2x4 to hold the pedal down :-0 but it's a stupid way to live, lol

speed bleeders on all four corners, it'll make things much easier.