What causes injectors to fire?

[Turbospec]

Recently got a new to me 86 van, so far I've put in:
-new coil
-newtome ignitor
-new fuel pump
-battery

Van has been sitting for 12 years, getting spark now, and fuel to rail.
Have tried searching

What tells injectors to fire in the van? Do they have a crank or camshaft position sensor? Or is it based off distributor?

[VanCo]

There is just one pickup, it is in the distributor. That sends a cam signal to the igniter. The igniter sends a modified signal to the ECU. The ECU then uses that signal to directly fire the injectors (negative trigger). The ECU also sends a modified signal back to the ignitor to fire the coil. On the positive side of the injectors there is a resistor pack to change the impedance of the circuit.

[Gaberrock]

I’m picking up a van with the same issue.

So the problem would lie in the distributor pickup, igniter, ECU, or the wiring in between right? As long as there is positive power to the injectors with the key on of course. Are there grounds that could bad and cause injectors not to fire?

[VanCo]

That is pretty much what is needed for spark and injector pulse. The ECU and all components involved will need the proper power and ground of course. The injectors are negative fired from the ECU, no other ground. Quickest way to see if the ECU is sending a pulse to the injectors is to use a noid light.