Hello everyone, I'm just finishing up a similar problem with fuel metering pumps and thought I'd share my findings.
Got this 803A from GP, they said it wouldn't start and made it sound like the reason was that the fuel hoses, filter housings and fuel solenoid were missing. When it arrived I immediately noticed the exhaust flap missing and thought "Oh Crap!" bet there's water in the motor. So sure enough, water in the center 2 cylinders and engine is frozen.
Took it apart, honed cylinders, cleaned up the rings, lapped the valves and put it together.
Go to prime the injector lines and not getting fuel out of any lines. I noticed the fuel shut off linkage feels like its not doing anything so I pulled the metering pumps 1 at a time... the last one I pulled was frozen in the fuel off position.
When I went to reinstall, I had a finger down 1 pump hole to try to align the rack and just couldn't get any 1 pump to drop in without binding up the rack.
After reading this post, I went back, installed 1 pump and then tightened the holding clamp down. once the pump was seated, the rack moved freely.
The problem was just as the guys mentioned above. If the pumps are not fully seated, the linkage will hit the underside of the block, causing the rack to bind up.
Thanks to rhurey for the pictures, it may have saved me from pulling my hair out!
Now I just need to clean and install last 2 pumps, then try starting it again...