Starter motors may experience intermittent cranking issues as they approach the end of their useful life. When it comes to starting your engine if your car won’t start, a slight hitting or tapping of the starter with a hammer usually works. This is because a starter solenoid becomes stuck sometimes which prevents starting of your engine. But, where to hit starter with hammer? In this guide, I’ll discuss how to tap a starter to make it work and start the engine. So, let’s get started.
Where to hit starter with hammer? You should slightly tap the starter solenoid body or starter motor body to activate the starter. When you hit a starter solenoid body, the stuck solenoid dislodges, makes contact with the starter motor, and allows current to flow through it. If the armature of a starter motor has a dead spot on it, hitting it with the hammer will move the armature into a slightly different position where it can make contact and allow the engine to start. While tapping a starter solenoid, have someone constantly turn on and off the ignition key. If you hit the starter too hard, it will damage electromagnetic coils, permanent magnets and carbon brushes. Tapping a starter with a hammer trick only works if the starter solenoid is stuck.
If your car won’t start and you hear a series of rapid clicking noises when you turn on the key, it indicates bad battery, ground or starter connections that are causing intermittent failures. If you hear a single, loud click coming from the starter, it means that a solenoid is trying to engage but it is stuck. In that case, you should slightly hit the starter solenoid with a hammer. To learn more, you can read my guide on car starts sometimes and sometimes it doesn’t.
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How Does A Starter Work?
A starter is a device that helps a car’s engine start. It is usually located on the side of the engine, near the flywheel. The starter is located close to the flywheel on the driver’s side of the engine.
The starter contains a small electric motor that turns the engine over, or “cranks it.” When you turn the key or push the button, the starter gear pops out and engages the engine’s flywheel. The starter’s motor turns the flywheel, which gets the engine moving. Once the engine is moving, it can generate its own power. So, the starter gear retracts.
A starter consists of the following main parts:
- Starter solenoid
- Electric starter motor
- Gear drive
The internal view of a starter is shown in the illustration below:
- Location of pinion shaft
- Rolling element of freewheel clutch
- Mounting flange
- Solenoid coil
- Contact bridge
- Battery connection
- Carbon brush
- Pole winding
- Reduction gear
- Engaging fork
- Meshing spring
- Freewheel clutch
- Stop ring
The starter solenoid has windings and a plunger. The winding gets magnetized when a current flows through it. The plunger inside a starter solenoid moves due to a magnetic force acting on it. That plunger acts as an actuator to move a pinion gear in front of the flywheel and close the contact bridge to transfer current to the starter motor.
The starter solenoid performs the following functions:
- Pulling the pinion to engage the flywheel
- Holding the pinion engaged with the flywheel during starting rotation
- Completing the electrical circuit from the battery to the starter’s brushes
- Causing the pinion to retract from the flywheel.
The starter solenoid has three terminals:
- First terminal gets a constant 12V supply from the battery.
- Second terminal connects with the ignition switch that feeds current to the solenoid when the key is turned on. It is also called S terminal.
- Third terminal supplies current from the first terminal to the starter motor terminal when the plunger inside a starter solenoid makes a contact bridge.
Electric Starter Motor
The starter motor provides the initial mechanical energy to the pinion so it can rotate. This, in turn, transfers its energy to the flywheel to start the engine. The electric motor section of the starter motor consists of the armature, carbon brushes, permanent magnets, electromagnetic coils, armature shaft, etc.
Next to the starter motor is a gear drive section. The gear drive section has a reduction gear drive and a pinion gear at the end. Reduction gear drive reduces the speed of the shaft and the pinion gear meshes with the flywheel.
If you need a video demonstration of the working of a starter, I found the following Youtube video helpful:
Why Does Hitting A Starter Make It Work?
Tapping or gently hitting a starter with a hammer can:
- Give enough of a jolt to the brushes to make a contact with a commutator
- Dislodge a stuck starter solenoid
- Push armature to a new position where it can make a good electrical contact
Hitting a starter with a hammer can dislodge a plunger of a starter solenoid that has been stuck due to the accumulation of dirt and grit around the plunger ends. So, if the plunger inside the starter solenoid is stuck in the “in” position, it will prevent the pinion gear from moving out and engaging with the flywheel when the ignition switch is turned to the “on” position.
Moreover, there are brushes in the starter motor that are made of either carbon or copper. They also wear out or rust develops on them, due to which they do not have a perfect electrical contact to transfer the electric current.
These brushes in the starter can also become stuck, due to which they can’t move when the armature rotates. So, these electrical contacts are jarred enough to get the circuit to complete which will cause the starter motor not to turn.
So, by hitting the starter motor area, the carbon brushes are moved back into place so they can make contact one more time with the commutator and allow electricity to flow.
Moreover, the copper contacts, which connect the positive cable to the starter winding, burn and leave a black residue that prevents the contacts from working properly. You can try cleaning the contacts with a wire brush until they are shiny and bright.
Another important point in a starter is a copper washer that is pushed into the two large contacts when a plunger is sucked into the starter solenoid under the action of a magnetic field. The contact of the copper washer allows electric current to flow to the starter motor. If the contacts or copper washer have bad spots, hitting the starter with a hammer can move the copper washer slightly where good electrical contact can be made and electric current can be transferred to the starter motor.
There are following important spots on a starter where you can hit a hammer gently to try to start your vehicle:
- Starter solenoid
- Starter motor
- Gear drive
While gently hitting the starter, you should have someone to hold the key in the start position.
The reason for gently hitting the gear drive in the starter is that the teeth on the front face of the pinion can be abraded, due to which they cannot properly mesh with the flywheel. By hitting the gear drive part of the starter, you can move the pinion from the vibration so that the teeth of a pinion in a better condition can face the flywheel.
How To Test A Bad Starter?
Before removing the starter from your vehicle, you should first check its connections. First, you should check the voltage across the positive terminal of the battery and the S terminal of the starter using a voltmeter. The voltage should be less than 0.2V when you try to crank the engine.
If the starter connection passes the voltage drop test, the next step is to test the starter.
To test the starter, you have to pull the starter out from your car. In some cars, the starter is located under the engine while in other vehicles, you will find the starter near the engine block when you open the hood. If the solenoid of the starter is working, the gear will come out of the motor casing to engage with the flywheel. If the starter motor is working, the gear will rotate as well. Sometimes, faults are in the armature of the starter motor that causes intermittent starting of the car.
I found the below video helpful to test the starter motor:
Symptoms Of A Bad Starter
- The starter motor doesn’t engage when you turn the key.
- You hear a clicking noise when you turn the key.
- The starter motor makes grinding noises.
- The starter motor smells burnt.
- The starter motor is very hot to the touch.
How Long Will Tapping The Starter Work?
Depending on how much a starter is damaged, tapping a starter may work until the parts inside the starter can break and lock the starter up. Usually, you need to tap the starter 2 to 4 times every week to make it work. But, it all depends on how much brushes and copper contacts of a starter are damaged or how badly a starter solenoid is stuck.
So, tapping a starter to make it work is not a permanent solution as the starter could make loud grinding noise if the starter gear would not engage the flywheel properly. It will further damage the pinion of the starter and can harm your engine.