I have a 1991 ford ranger a few weeks ago i stoped at a local gas station and my rpms droped and my truck quit , After test my coils I am not getting fire from them ,one wire is showing hot cgoing to my coil ,,,,I have changed The computer ,Crank sensor ,1 coil ,ignition,spark plugs and wire.....I am stumped and am runing out of parts to change any Help would really be appreciated... THANKS