Do you need the engine running to bleed brakes on a 1990 ford ranger 4.0?

No, you generally do not need the engine running to bleed brakes on a 1990 Ford Ranger 4.0, or most vehicles for that matter. The brake system is hydraulic, and the pressure is generated by the pedal, not the engine. Having the engine running might slightly increase pressure in the system but isn't necessary and could be potentially distracting or even dangerous (e.g., accidentally hitting the gas pedal). Bleeding the brakes is best done with the engine off.