1978 Ford Kencraft manual/expertise

Are you talking about the starter solenoid? if so there is not really much to it, from the start wire from the ignition switch it goes to the transmission neutral safety switch, from there to the Solenoid under the hood. the Solenoid is a common fail point have jumped many over the years in various Ford products to get home or to the parts shops. There is two small terminals one marked "S" other marked "R". R is the Ballast resistor by pass for the ignition to supply 12v for the ignition coil to give hotter spark for starting, the S terminal is the Start wire from the transmission safety switch, Jumper the S to the positive terminal of the battery should spin the starter. if the solenoid clunks and starter does not spin , using a jumper cable jump across the two large terminals of the solenoid and the starter should spin now, if it does, replace the solenoid, if it does not check the wire from the solenoid to the starter, if it good replace the starter..