I mainly used clear tubing so that I could easily compare the volume of fuel flowing through each injector. This was after running them through a DYI back flush process. Whether the flow rate was to spec or not I had no idea, but I figured if all four were equal, or "close" to equal, then there was a good chance the flow rates were close to spec. Being able to witness the spray patterns turned out to be a bonus I hadn't thought about.

Setting up for the test, I pulled the distributor out of the engine, removed the cap, and re-connected the trigger points connector. Turning the ignition on activated the fuel pump and D-jet system. Then I spun the distributor rotor as fast as I could with my finger - spin, spin, spin, - and watched the injectors spray into the clear tubes. With no vacuum being applied to the MAP sensor the system calls for a high fuel flow rate through the injectors. I sucked on the MAP hose to simulate different engine loads along with propping the throttle plate open or closed while spinning the distro resulted in varying amounts of injector flow. As I recall, quickly opening the throttle alone resulted in an "acceleration shot" of fuel from the injectors. It was somewhat interesting. So now I was, in effect, performing a poor man's test of the entire D-jet system.

A more crafty person would probably arrange a way to spin the bistro with a drill motor and use a vacuum pump to drive the MAP through varying vacuum levels so they don't have to suck on the hose.