ok here goes, if i had no output from an injection pump i would loosen the fuel line that supplies fuel from the fuel filter(secondary=big one)to the ip,crank the engine and see if it pumps fuel.if no i got to fix the fuel pump or the fuel lines or put some fuel in the tank. if yes i would retighten the fuel line i loostened,i would then loosten the return fuel line from the ip and again crank,i should see fuel there also but controlled by the relief valve at the ip pump. the ip needs it fuel to be under pressure and if the relief valve dont close at the correct pressure it just wont work right.
assume i have fuel to ip,fuel from the ip then i have to know the ip is being turned,assume its being turned,i have to remove the top most fitting on the ip after the pressure line to injector has been removed,this is the check valve to hold pressure on the injectors while engine is waiting for the next firing,these valves not holding will cause no starting to very slow starting. now i take a straw and place it down to the power plunger of the ip where i removed the check valve assy, again crank the engine, i should see the straw work up and down about 1/4 inch.
assume all test have passed the test,then i probably call my self a few choice words and go back and pull the vac shut off line from ignition key(usually the brown one) off the shut down valve and again crank the engine and listen to the clatter-clatter.
course i would have to know my compression.
hope this helps
71 old cars