How to Wire a Ford Solenoid | It Still Runs A Ford starter solenoid is one of the key components to the starting system of most older Ford vehicles. It's essentially a big relay, which provides power from the battery to the starter motor when the ignition key is turned over, starting the vehicle. These solenoids are typically the first thing that goes out Starter motor wiring | Classic Ford Forum Just incase you didn't know (if you did then ignore), the small cylinder bit on the top of the starter motor is a solenoid. It's job is 2 fold. Firstly, when it receives power from the ignition switch (when turned to the start position), the energised solenoid pushes the starter motor shaft forwards to engage the starter teeth with the flywheel.