fuel injector

We didn’t a 2.5 swap from a 91 S10 into the wife’s Vega, and no start. Have spark and fuel to the tbi, but nothing from the fuel injector. I’m on my way to get a new one, but wondered what sort of signal it gets to operate and how to test that signal and the injector itself?

I know this sounds dumb, but I don't know how many fuel injectors to order. I have a 1992 S10 with the 2.5L 4cyl RWD 5-speed, ext. cab. I know there's not 4 because it has TBI but after trying to find how many, I can't find anything for this specific year whether it has a single injector or...