When you turn your key, the starter is the thing that cranks over the motor, so it can begin internal combustion. The gear on the starter engages the gear on the flywheel. The flywheel is bolted to the crank shaft, which is an integral part of the engine. Internal starter design has changed dramatically over the last 2 decades. Words like “permanent magnet, gear reduction, and balanced armature” are not just entering into the field, but are a mainstay. All manufactures now are designing planetary gears for torque, and permanent magnets for their resistance to extreme hot and cold temperatures and ability to provide reduced amperage draw on the battery.
The best thing about starter design is the fact that the gear on the bendix (drive) must be engaged in the flywheel BEFORE the motor will start to spin. The solenoid, which is mounted on the starter, magnetically pulls a metal plunger. The plunger is attached to a lever arm which pulls the drive at the other end of the lever. Then, after the drive goes into the flywheel, the contact is closed in the solenoid by the plunger itself. This is a high amp contact, connecting the battery positive cable to the motor terminal on the starter.
The most common misconception is about the solenoid on the starter. People think that when you turn your key, and the starter has all the proper voltages, if the solenoid does not pull out the bendix drive, it must be a defective solenoid. This is rarely true. That scenario is mostly a defective starter. Here’s why: In order for the solenoid coil to work, the pull in coil must have a good ground. The coil gets its ground from the field coil, which gets its ground from the brushes riding on the commutator. So if there are faulty brushes or dead bars on the commutator of the armature, the solenoid coil won’t energize.
Since the beginning of mechanics crawling under cars, it has been very common to hit the starter with a hammer while someone holds the key on. This method, although thousands of people can testify salvation from the tow hook, needs to be reconsidered. All Ford, GM and most foreign manufacturers are using magnets instead of copper field coils. This is great for the ecologists, who resist massive use of the world’s natural copper resources. Man made magnets are produced massively with little damage to our environment. The testing of the magnetic field in extreme heat and below zero temperatures is far superior to the previously popular copper/iron set up. The thing is: YOU CAN’T HIT IT WITH A HAMMER! Magnets are extremely brittle, once they break, they’re done. A little tap with a big wrench or a screwdriver is all that is needed to get you started one more time.