Where is the computer hookup for 1986 Ford Ranger?

There wasn't a standardized "computer hookup" in the way we think of OBD-II ports in 1986. 1986 Ford Rangers didn't have a readily accessible port for connecting a laptop or diagnostic tool like today's vehicles. Diagnostics were done through a connector usually located under the hood, near the battery or firewall, often requiring a specialized Ford scan tool connected to various pins to read diagnostic codes. The exact location and the connector type varied slightly depending on the engine and options. You'd need a wiring diagram specific to your 1986 Ranger's engine (e.g., 2.3L, 2.8L, etc.) to pinpoint the diagnostic connector.