For a car or truck to be reliable, it will need a sophisticated electrical system with both low and high power circuits. The circuits are capable of sending low voltage to simple items like interior lights or high voltage to crucial components like a starter motor. But how does your vehicle system manage this differentiation, and how can a starter motor crank something as heavy as a vehicle engine?

Starting Power

When you turn the ignition key on the dashboard, this opens a simple, low voltage circuit that will provide power to a special component known as a solenoid. This is effectively a relay that will then open a much more powerful electrical circuit connected directly to the battery. The solenoid will feed this high voltage through to the adjacent starter motor so that it can turn with enough force to crank over the engine. Essentially, cogs on the end of the starter motor engage with the engine's flywheel to activate the crankshaft. At the same time, fuel is fed to the top of the combustion chamber which, when ignited, keeps the process going.

Signs of an Issue 

The solenoid and starter motor are crucial components. Yet as with everything else, problems can arise, and they may not function correctly. Your first indication may well be an outright failure. In this case, you may turn the key in the ignition and only hear a solitary "click." The radio and dashboard lights appear to be functioning correctly, so this is not a battery issue. Instead, either the solenoid, the starter, or both have likely failed.

Listen carefully when you turn the ignition key. Do you hear a single click or repeated clicking? If it's a single click, the solenoid is trying to open the high-voltage circuit but is failing to do so. If you hear repeated clicking, then the solenoid may be doing its work, but the starter motor may be dead.

What to Do Next

If you don't hear any clicking, check to see if a fuse is blown first. In this case, there could be other problems with your electrical system as well, and you should consult with a mechanic for further advice.

In every case, you should always buy high-quality replacement parts. The solenoid and the starter motor live in a hostile environment and are subject to high temperatures and degradation. If you buy the best parts, you're less likely to suffer a failure like this again soon. To learn more, contact companies that sell Toyota spare parts.