What is a box in the starter and why do I need it?

How to check the starter box with their own hands in 15 minutes



Easy starting of the car engine is possible only if each part, which transmits torque from starter to crankshaft, works perfectly. The starter rocker arm is one of the most important elements of this system. It is important for every car owner not only to get comprehensive information about the technical device and the principle of operation of this mechanism, but also to learn how to determine its malfunction.

What is a bendix on the starter and what it is for

The starter bendix is a device, the principle of operation of which is similar to the work of the clutch installed in the transmission of a car with a manual transmission. In contrast to the more massive system, which serves to smoothly transmit torque from the crankshaft to the wheels, the overrunning clutch on the starter performs its function for an extremely short time. In addition, the disengagement from the idler pinion, which is located on the crankshaft flywheel, should be carried out at the very beginning of independent operation of the starter. These requirements are the reason for the peculiarities of the bendix design.

On the state of the starter bendix depends not only the ability to easily and quickly start the car. Significant deviations in the work of this part can lead to failure of the gears, which transmitted torque to the crankshaft. Almost always, if one part fails, soon go and mating parts.

The construction of the starter’s bendix

The bendix is a compact part installed on the starter shaft. This element is made of a durable metal alloy. The part has to work under increased mechanical stress, which explains the need to use wear-resistant materials.

The design of the bendix is as follows:

  • Master and slave cage.
  • Casing.
  • Support cups.
  • Clamping spring.
  • Rollers.
  • Roller springs.

The casings are mechanically connected to each other by the rollers, which are pressed down by the springs and drive them into the narrow channels of the structure. Due to this feature, the clutch starts working only when the engine starts. After cranking the engine, the clutch is immediately disengaged as soon as the engine starts to run on its own.

The design of the rocker arm

The principle of operation of the bendix

The principle of operation of the starter bendix is based on the inertial forces that cause the position of the drive pinion to change, at different modes of operation of the engine starting device. Due to the presence of this part it is possible to reliably protect the electric motor, as well as the rotating elements of the engine from the “unauthorized” activation of this mechanism.

How the starter rocker arm works

The rocker arm on the starter works in the following way:

  • The moment the ignition is turned on and the key is moved to the end position, electrical current is supplied from the battery to the starter motor.
  • The starter motor starts to rotate and drives the shaft, on which there are screw notches along which the coupling moves under its own weight. As a result, the drive pinion on the bendix engages with the flywheel pinion.
  • After the engine is started, the bendix pinion begins to rotate rapidly and move inside the starter housing.

The stability of the bendix mechanism is also due to the presence of a buffer spring, which significantly softens the moment of contact of the drive pinion with the flywheel splines.

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Signs of failure of the starter rocker arm bendix

The starter bendix is a very reliable part, but with prolonged use of the car, this mechanism can also fail. Almost always such an undesirable event is preceded by various manifestations that are impossible not to notice. The most characteristic signs of bendix failure:

  • A noise during the start of the engine.
  • The engine crankshaft does not rotate.

If the bendix is not completely defective, the sign of the malfunction of the part may appear periodically. Sometimes, this element meshes with the idler gear, but after a short run slips with a characteristic sound effect.

If there are signs of bendix failure, you should not postpone repair for a long time. If the damaged part will not be repaired or replaced in time, it will be necessary to perform a more complex operation associated with the installation of a new flywheel pinion, damage to which will not allow normal operation of the car, even after the purchase and installation of a new overrunning clutch.

Defective locking bolt

Possible causes of failure

The starter overrunning clutch consists of a small number of parts, so there can be several causes of breakdowns. The most common cause is wear on the inner rollers. Reducing the diameter of these parts leads to the inability to reliably meshing the moving elements. Sometimes, flat surfaces can form on the rollers, which also prevent normal operation of the coupling.

All the working surfaces in the meshing can wear out over time. Such malfunctions of the starter bendix are natural, but if they are present, the part can not be restored.

How to check the starter bendix

If the car engine does not start or the moment of starting is accompanied by unpleasant metallic sounds, then before making a decision about repair or replacement, it is necessary to check starter’s bendix. The initial stage of diagnosis can be based on the auditory perception of the malfunction of this part. To use this method, you need to be in the immediate vicinity of the engine, so it is recommended to involve an assistant to the event of audible determination of the quality of the bendix. If at the moment of starting the engine the starter motor is running and a metallic squeal is heard from the location of this part, it is highly probable that the overrunning clutch is defective.

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You should not rely solely on your auditory organ when checking the bendix. After detecting noises localized in the area where the starter is located, it is necessary to dismantle this part and carefully inspect it. The first action, which allows you to immediately determine the possibility of further use of the part, is the rotation of the drive pinion in different directions. If the movable element rotates in both directions, the bendix will need to be replaced. The presence of worn out teeth also indicates the impossibility of further operation of the part. In the presence of backlash on the armature, as well as excessive wear of the fork, the bendix will need to be replaced with a new part.

Starter bendix repair

The cost of a new bendix even on the expensive car brands is relatively low, but as an experiment, you can try to restore the part with your own hands. It should be noted the fact that in the presence of excessive wear of the cages, the repair operation is almost impossible. It is impossible to increase the metal of these parts, but if only the rollers in the clutch have undergone a change in geometry, it is possible to repair the part by replacing these elements with pieces of metal that are suitable in diameter. For this purpose, for example, pieces of drill bits of a suitable diameter or pieces of nails of a suitable size can be used. In the latter case, in order to increase the strength of the metal, it is advisable to harden it so that the outer surface gains more strength and the metal inside is not too brittle.

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If the roller springs or compression springs are broken, parts of suitable stiffness and diameter can also be selected for replacement. If there is another faulty part, it is possible to combine the elements so that the result is one serviceable bendix. The presence of several broken elements significantly increases the possibility of such borrowing of well-preserved elements.

Bendix bars disassembled

How to disassemble the bendix

If it is decided to engage in repair of starter bendix, it will be necessary to disassemble this part. This operation is performed as follows:

  • Remove the starter from the car. Before performing this operation, disconnect the battery terminals, unscrew the fasteners and disconnect the wires from the part.
  • Unscrew the bolts fixing the starter and disassemble the housing.
  • Remove the retractor relay.
  • Disassemble the bendix.

To disassemble the bendix it is necessary to remove the retaining ring, remove the washer and separate the outer and inner part of the element. Before reassembling the bendix gears should be washed in acetone, dried and lubricated with thermal grease.

How to change the bendix on the starter

It is much easier and more correct to install a new part to replace a worn one. If an original spare part is purchased, then after correctly performed work, the duration of operation of the node can be counted in years. At the initial stage of repair, all operations are identical to the repair of the node with your own hands. It will also be necessary to carefully remove the starter, disassemble it and disconnect the bendix. It is not necessary to disassemble the part, immediately after performing the disassembly work, you can proceed directly to the installation of a new bendix.

Replacement of the starter bendix

After the old part is done, work on the installation of the new bendiks is carried out in this sequence:

  • Lubricate the shaft with thermal grease.
  • Install the part on the shaft.
  • Put the washer and the lock ring on the shaft.

Difficulties when installing the bendix can often be observed when installing the retaining ring. This part can be put in place with a pair of impact wrenches or sliding pliers. Care should be taken when performing this operation, as the resilient element may spring back a considerable distance.

After the new bendix is installed and the starter is assembled, it is recommended to test the operation of the part without installing it on the engine. A car battery and cigarette lighter wire can be used for this purpose. It is important to observe the polarity when connecting the contacts, otherwise the engine will start rotating in the opposite direction. In order not to make a mistake it is recommended first to connect the “minus” to the ground, and only then connect the “plus” to the appropriate contact on the body of the retractor relay. When performing this operation, you must be careful, because at the time of the starter on the wires flows current of great force, so you can get severe burns, if you do not adhere to safety rules.

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How to remove the bendix

In some cases, before removing the starter bendix, it is necessary to perform some actions that will greatly simplify this task. For example, in order to remove the old part and install a new part, it is required to remove the starter from the car. If this operation has not been carried out for a long time, the bolts of the electric motor may become so “riveted” to the body that it is impossible to unscrew them without risk of destruction. In such a situation, you should use a penetrating lubricant, which should be applied to the bolt and wait 15 – 20 minutes. You should then tap the bolt heads with a small hammer and attempt to unscrew them. As a rule, such preparation and careful actions during disassembly allow the fasteners to be preserved for future use.

If there is no grease, the “acid” bolt can be loosened by heating. A gas torch can be used for this purpose. It is important when using this method not to overheat the metal so as not to degrade its mechanical properties.

How to remove the lock washer

Some difficulty may also be encountered when removing the retaining ring that holds the bendix on the shaft. It is recommended that a special mandrel be used for this work. If it is not available, you can use thin screwdrivers to perform the operation, as well as round pliers, which should be used as a puller.

The starter belt is a very important part of the car, but this part is relatively inexpensive. For example, for VAZ cars, you can buy a new part for less than 1 thousand rubles. At the first signs of trouble with the bendix it is recommended to immediately contact a car service to perform repairs or perform the installation of a new part yourself. Failure to perform the repair operation on time may lead to very undesirable consequences. The lack of a reliable drive between the starter and the crankshaft can become the most dangerous at the time when you need to quickly start the engine in an emergency situation.

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To start the engine of a car, the driver today simply turn the ignition key or press a button. With this simple action, he activates a chain reaction in which, in addition to the motor itself, the starter and the battery also take part. An important role in this process is assigned to a device called a bendix. How it works, why it needs and what to do in case of its failure, we will tell in our article.

What is a starter bendix and what it is needed

How does starter rocker arm bendix look like?

What does the starter bendix look like.

The bendix or overrunning clutch is an element of the starter that is structurally a small clutch. It consists of a pinion, a pair of metal cages, clamping and buffer springs, and a retaining ring. Everything is located in the body of the starter and is actually a part of it.

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First of all, the bendix is designed to take the load off the starter and protect it from damage when starting the engine. This mechanism can significantly extend the life of the starter. In addition, it helps to start the engine almost silently, which positively affects the comfort of car operation.

How the starter rocker arm works

The bendix working principle is based on the inertial action. With the toothed shaft it is connected to the flywheel of an internal combustion engine and transmits to it the energy of rotation of the starter motor. As soon as the engine was started and the number of revolutions significantly increased, the bendix takes all the load on itself, not allowing the increased torque to go back to the starter. For this purpose the clutch is equipped with special grooves in which the cylinders are located. This mechanism allows for a rigid coupling when transmitting torque from the starter to the engine and idle clutch rotation on its own shaft when the engine has already gained high revolutions. All this is necessary in order not to damage the starter, since the load of more than 80-100 revolutions per minute significantly reduces its life.

starter box in disassembled condition

The starter’s rocker arm in disassembled condition.

Also in the design of the bendix is a special buffer spring – it is thanks to this mechanism the start of the engine is soft and quiet. In its absence, the hard contact clutch gears with the flywheel not only would give itself to the knock and rattle from under the hood, but also very soon would have led to the output of the starter.

After the engine is started, the clutch will gradually slide down the splines and disengage from the flywheel until the next engine start.

Signs of failure of the starter rocker arm bendix

The main sign of failure or partial failure of this unit are uncharacteristic noises when trying to start the engine. This may be a metallic squeal or sounds of sharp impact of two heavy parts against each other. It is very important that this happens exactly before the engine began to produce torque on its own, for if the noise is heard already when the engine is running, the source of the problem is probably already in another node of the car.

starter motor structure and bendix location

The starter unit and the location of the bendix.

If the acceleration clutch is completely out of order, then instead of a measured rumbling of the motor you will hear only the noise of the starter motor turning without result. As practice shows, this does not happen immediately, but gradually, if the driver ignores the more minor symptoms of malfunction.

Read also : How the start-stop system affects the starter.

How to check the starter bendix

Checking the performance of the bendix is possible without disassembling the car. Of course it is difficult to diagnose the malfunction by its sound and if you are not experienced in this matter, you have a great chance to make a mistake. If when you turn the key in the ignition switch you will hear clanking sounds from under the hood in addition to the cranking of the starter, most likely the gear teeth are worn and the device can not catch the flywheel of the engine.

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In any case, if you identify a malfunction by ear, it will be necessary to carry out a visual inspection of the device, as well as its replacement if it is impossible to fix the problem. First it is necessary to remove the starter, then the bendix itself is carefully removed from its housing. The main point to pay attention to during the inspection is the integrity of the teeth on the clutch pinion. If they are seriously chipped or otherwise damaged you will have to buy a new part. During further diagnosis, be sure to check to see if the part of the clutch that is adjacent to the flywheel can rotate idle in one of the directions. If the bendix is jammed and both of its cages rotate together in both directions, you will also have to replace this acceleration clutch to avoid starter breakdowns.

In addition, check the tension of the buffer spring, since it is its malfunction that can cause signs of deformation on the gear teeth. If there is backlash in the bendix design, it also affects its performance and an increased level of wear of the starter parts.

In some cases, the appearance of extraneous sounds can be associated with the ingress of dirt on the working surface of the bendix, as well as inside the body of the device. When disassembling the starter, carefully check the equipment for traces of dirt, dust and other foreign substances. If necessary, wipe the gear teeth as well as the accessible cavities of the housing.

Read also : Why the starter cranks but the engine won’t start. A breakdown of the possible causes.

How to change the bendix on the starter

Replacing the bendix in many cases is the best option, even with the failure of its individual parts. The fact is that during operation all parts of the device wear out with approximately the same intensity and replacement of one of them does not guarantee long operation of the bendix in the future.

So, to replace the bendix, the starter has to be removed. Then you need to open its housing and remove the relay, only after that you can get to the bindiks. It is held on the axle by a washer and a retaining ring, as a rule, to remove them you will have to struggle a bit, especially to remove the ring.

Then we proceed to the stage of installation of a new part. Beforehand it is better to clean the internal space from the accumulated dirt, as well as a good lubrication of the moving and mating parts of the structure. The most difficult part of the replacement process will be the installation of the new retaining ring, to make this job as easy as possible, use special sliding pliers. Tighten the bolts on the starter housing and install the unit back into the car. Test the engine a few times, if there is no noise/cranking, then you have done everything correctly.

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