I have 2 tips for you.

#1 Poke some LED's down into the backside of the injector clips. You should be able to get them to contact the leads, and still have it installed on the injector. This will give you a visual of when / if the ecu is firing the injectors. If it doesnt light up when you first try it, flip the LED around to make sure the polarity is correct..... Tis a diode afterall. This will tell you if the ECU is firing the injectors or not. If not, you have some sort of issue in the ECU, or wiring, or sensor. If it IS firing them, then you have a fuel system issue. Clogged lines, clogged injector screens, pump that is not putting out enough pressure, clogged filter.... etc. I know you said you pulled the line off, and it pumped fuel, BUT, it may not be putting out the required pressure.

#2 There's no replacement for a fuel pressure gauge in this instance, BUT, try to "kink" the rubber line on the return from the motor.... to make it build up higher pressure inside the rails. You should be able to "feel" the pressure build up inside it.