A starter is an electric motor that can crank an engine by pulling power from the battery. To make this happen, the starter motor must be connected to a solenoid that controls the electrical connection between it and the vehicle’s battery. The solenoid is made up of two coils of wire wrapped around a moveable core that acts as a switch to connect and close the electrical connection.
The Solenoid Wiring
Whether your starter is mounted on the front of the engine or a remote-mounted device, it needs to be hooked up to the solenoid wiring to ensure it works properly. Thankfully, most starter solenoids are easy to wire and have all the necessary connections in one place.
Starter Solenoid Types
There are 2 common types of starter solenoids: those that are attached to the starter and those that are not. In either case, you need to know how to wire these devices to help you make the most of your starting process.
The first type is the on-starter solenoid that is directly mounted above the starter. The solenoid has two large connection points where you’ll need to connect the positive battery cable or terminal and also the starter feed wire.
This type of starter solenoid has an additional small post that accepts the purple wire from the engine harness, which is the main trigger for the starter to fire. This wire carries current from the ignition switch, often via the neutral safety switch, down to the starter to activate it.
When the starter is engaged, it pushes forward on a plunger that engages a pinion. The pinion is a special combination of gear and springs that will spin the engine, starting it.
Once the pinion is engaged, it will extend out into the gearbox housing and will be connected to the flywheel. Once the flywheel is spinning, the starter will then be activated and it will begin the engine’s combustion process.
If you have a remote-mounted starter, your solenoid will be located in the engine block, or somewhere else near the battery. For this reason, the solenoid wires are different than for on-starter types.
The Starter Relay
A relay is a simple circuit that combines the minimal current from the ignition switch with the high current output of the starter motor. The relay uses this minimal current to induce an electromagnetic force inside the coil winding of the relay, which then moves an armature and completes the circuit that powers both the starter motor and the starter solenoid.
The most common problem with the starter relay is corrosion of the wires or its connection to the battery. If the wires or the connection to the battery are corroded, they will cause resistance and this can prevent the relay from working correctly.
To check for this, you’ll need to remove the starter solenoid and use a digital voltmeter to measure the voltage between the relay’s “B” and “M” terminals. If the voltage is below a certain value, it means that the relay isn’t functioning correctly and needs to be replaced. If the voltage is above a certain value, it means that the wiring to the relay is corroded or otherwise has an issue and will need to be repaired.