1991 Mazda b2600 fuel injection

It's an electrical circuit. There is an engine management unit/computer. There are also sensors that give the computer information regarding engine temperature, vacuum, engine speed and position, and more, that the computer uses to determine when and how much fuel to give the engine.

Which sensor tells engine position?

There's a crank position sensor that feeds the engine management computer.

Where is it on a 1991 Mazda b2600i..2.6 liter?

My reference shows it at the front bottom of the engine.

Will a bad break sensor cause constant power to both sides of the injector when the engine is rolling over?

The brake system has nothing to do with the fuel injection system.

I'm sorry not a break sensor I meant to say crank sensor.

No. Power to both sides of the injector is either faulty wiring or a bad controller.

What is the controller and where is it?

It's a little metal box with or two big connectors going to it. It is located inside the passenger side footwell area behind the plastic kick panel cover.