BOSCH starter — design description

A small electric motor called a starter is used to start an internal combustion engine. In order for the car engine to be started, the starter must spin the engine crankshaft to a frequency of at least 300 rpm. This can only be done with a perfectly working starter and a sufficient charge of the battery.

The starter consists of a drive housing, a pole housing and a collector housing. An armature is located in the pole housing, and a collector and a brush holder are located in the collector housing. There are brushes in the brush holder, which, although slowly, but constantly wear out. With a large wear of the brushes, the perfect operation of the starter is impossible.

The gear drive is located in front of the drive housing. When, when the starter is turned on, voltage is supplied to it from the battery, the traction turn located on the starter housing, through the drive enable lever, pushes the gear along the screw slots on the armature shaft to the flywheel ring gear. As soon as the pinion reaches a stop on the end of the armature shaft, it engages with the flywheel ring gear. In this case, the traction relay turns on the electric circuit of the starter, and now it can crank the engine crankshaft to the starting speed. As soon as the engine starts, the flywheel ring will begin to rotate the gear faster than the starter shaft rotates, and, having disengaged from the flywheel ring, it will move along the screw splines of the shaft to its original position.

Since the starter draws a lot of current when starting the engine, when servicing the engine, it is necessary to pay attention to the perfect connection of the wires. Remove corrosion at wire connections and lubricate with acid-resistant protective grease.


Engines are equipped with starters of different power, manufactured by different companies (BOSCH, MAGNETIMARELLI, NIPPON-DENSO) This must be kept in mind when replacing the starter.

Attention: The starter, depending on the type, is an exchange unit. This means that the defective starter is accepted by the manufacturer as payment for the purchase of a refurbished or new starter, and therefore the old starter should be taken to the store with you.