The system won't build any significant pressure with the fuel injector lines removed. If you want to see a high pressure spray you'll need to remove the injectors from the engine so you can see them and crank it that way. Your injector pump is the absolute last thing to check after you're positive every other thing is checked and working including compression, air filter, valves, fuel to pump, etc. Mainly because they don't fail often and they are expensive to have rebuilt. However, they can be tested for a reasonable price at most diesel injector pump service shops if you are dead-set on determining if that is the problem.