A diagram of what component?
try autozone.com they have free online manuals
A wiring diagram for a 1994 Ford Ranger can be found in the Chilton's manual for that vehicle. You can also find this wiring diagram at most auto parts stores.
your local ford dealership
You can find a fuse panel diagram for a 1986 Ford Ranger XL in the owner's manual. You can also find it at select auto part stores.
Call your local dealer.
Owner's manual, or Library.
where can i find a vacuum line diagram for 1989 ford 2.9 liter engine
It should be in the owners manual.
autozone.com has free online manuals
You can find a 1987 Ford E1 50 vacuum operated heater control diagram at your local Ford dealership. Most local libraries will have Ford service manuals with the diagram.