Vehicle starters: role, operation, and testing

An essential component for starting any combustion engine, the starter motor converts electrical energy from the battery into mechanical energy to start the engine. Indispensable for initiating combustion, it can vary between vehicles in terms of power, position, and technology.

Identifying a starter motor problem involves a series of simple tests, which must be carried out methodically and carefully. This guide details its role, how it works, its location, and the steps to diagnose faults.

How does a starter motor work and what is it used for?

The purpose of the starter motor is to initiate the self-powered rotation of an internal combustion engine using an external power source. Once the driver has turned the ignition key, the starter motor engages. The battery must be in very good condition and have sufficient amperage to meet the power requirements of the starter motor. Starter motors are available in 6, 12, and 24 volts, depending on the engine.

The starter motor consists of a relay, also known as a solenoid, a starter, an armature, a set of coils or inductors, and brushes, also known as carbon brushes, which act on the armature commutator.

In short, the starter motor converts electrical energy from the battery into mechanical energy to start the engine. Without it, it would be impossible to start a vehicle without resorting to manual methods such as the crank handle on older engines or push starting.

Where is the starter motor located on a vehicle?

In general, the starter motor is located near the combustion engine, as it must be directly connected to the flywheel in order to drive it. Its position varies depending on the type of vehicle, model, and engine configuration.

Location of the starter motor on a car with an internal combustion engine

The starter motor is often located at the junction between the engine and the gearbox, where the flywheel is located. It is usually placed below or next to the engine. Its position therefore sometimes makes it difficult to access without dismantling other parts of the vehicle.

Location of the starter motor on a motorcycle or scooter

On a motorcycle or scooter, the starter motor is usually attached to the engine block, often on one side. On some older or basic motorcycles, it may be replaced or supplemented by a kick starter, i.e., a foot-operated starter.

The main differences in starters depending on the type of vehicle

The starter will differ depending on the type and model of vehicle. The main differences are as follows:

The size and power will not be the same for a heavy goods vehicle as for a motorcycle. This is because the starter is sized according to the size and power of the engine.

The accessibility of the starter motor increases with the size of the vehicle; the larger the vehicle, the easier it is to access this component.

Some motorcycles and older vehicles have alternative systems such as manual or hybrid starting systems.

How to test a starter motor?

Testing a starter motor can help you diagnose whether it is responsible for a starting problem. Here are the main steps to follow, with or without starting, to carry out tests.

Checks before testing a starter motor

Before testing the starter motor itself, it is important to check the following points:

Check if the battery is low or dead, as this is the most common cause of a silent starter motor.

Make sure that the battery terminals, the cable going to the starter motor, and the ground are tight and clean.

Pay attention to the noise when starting: a click without rotation indicates that the starter motor may be blocked or the solenoid may be faulty; no noise at all indicates a dead battery, a broken relay or cable; and if there is rotation without engine drive, the starter motor pinion or ring gear may be faulty.

Testing the starter motor with a voltmeter

Connect a multimeter to the positive terminal of the starter motor (large cable coming from the battery) and a ground.

Ask someone to turn the key: the voltage should remain close to 12 V.

Then test the small control terminal: ignition switch/solenoid wire. It should receive 12 V when the engine is started.

If there is no voltage, there may be a problem with the relay, fuse, or key switch. If there is voltage but the starter motor does not respond, then the starter motor will likely need to be replaced.

If your vehicle's starter motor does not respond despite a functional battery and correct voltage, then it is likely the cause of the fault. A test on a garage workbench will confirm whether it is functional or needs to be replaced.

To find a new, high-quality starter motor that is suitable for your vehicle, Wagendass offers a comprehensive catalog. Testing a starter motor can help you diagnose whether it is responsible for a starting problem. Here are the main steps for testing, with or without starting.