More often than not, your car turns over smoothly when you start.
If it fails to do so, then it might be the case when you hear the annoying clack- clack- clack, – machine-gun sound from under the hood and the car fails to turn over.
If you hear this sound then it may be that the car starter, alternator, battery, or a combination of them are faulty.
Being able to accurately locate the faulty component not only saves you time but also the expense of investing in car parts that you may not need.
So, in this post, I’ll share some insights into why the car may make the stuttering – machine-gun sound, and also suggest some possible fixes.
Quick answer: If your car makes the stuttering machine gun sound and fails to turn over, the more probable cause is that the battery is weak and is not able to provide the required power to the starter motor to start the engine.
While this is usually the case, it may as well be because of loose cable connections that do not make firm contact with the battery.
These should be the first places you check before conducting other checks.
There are several possible causes why you may be hearing the machine gun sound from under the hood.
The possible causes are listed in increasing order of elaborate checks.
Read on for other possible causes of the machine gun sound.
3 Reasons Why your Car may make the “machine gun” Sound
It is better you work through them starting from the easiest to the more detailed checks for faster troubleshooting.
#1. Loose or corroded battery terminals. These increase the resistance between the battery posts and cables and result in high voltage at the point of connection.
This in turn reduces the amount of power available to the starter and stops it from starting properly hence the machine gun sound.
Confirm that the cable connections are firm and clean. If there is a sign of corrosion, clean it and make sure the battery clamps make firm clean and firm contact with the battery posts.
To clean corrosion off battery terminals, mix baking soda with warm water or any other good quality battery cleaning solution then pour over the battery terminals.
You may also be interested in learning more about why batteries corrode and how to remove the corrosion
#2. Dead or drained battery. A drained or dead battery is not able to supply enough power to start the car.
You can confirm if the battery is drained by measuring the battery voltage as a quick test.
A fully charged battery measures about 12.6 V. At 12.4V or below, the battery needs to be charged.
It is also possible for the battery voltage to be reasonably high yet it cannot maintain enough charge when accessories are connected.
To check for this you can fully charge the battery and then switch on the headlights.
Depending on the battery capacity, you should be able to power the lights for at least an hour at least and started the car.
If it is considerably less, say 20-30 min, then you might have a case of a failing battery.
#3. Starter solenoid contacts not closing properly. If the starter is damaged and the contacts are burnt or worn then the starter can produce the machine gun sound.
Why the Starter makes the “machine gun” Sound
This happens when on turning the ignition, the solenoid is engaged and switches on power to the starter motor.
The heavy power drawn from the battery by the motor causes the battery voltage to drop significantly, “starving” the solenoid of power and disengaging it.
When the solenoid is disengaged and the motor disconnected, the battery voltage rises again, is high enough to engage the solenoid and starter motor and so the cycle is repeated.
It is this continuous process that produces the clack-clack, machine gun sound.
How to Check if a Car Starter is Faulty and Should be Replaced
Some signs that can point to a bad starter (not always confirmatory) and need for it to be inspected are:
- the engine cranks too slowly when an attempt to start it is made
- the starter may rotate but does not crank the engine
- the starter does not stop rotating
- the engine does not crank
- there’s an unusual noise from the starter.
You can do a visual inspection of the starter. If you observe and note that the magnetic switch contacts or brushes are worn, starter gear teeth are worn or the starter motor windings are shorting then it is time to replace the starter.
Does hitting a Car Starter make it Work?
If you try to start the car and all you hear is a click by there is no cranking of the engine, then it may be that the starter is stuck.
Whereas some people recommend hitting the starter to free the controls in it, this has its associated risks that may not only damage the starter but other parts of the electrical system.
Damage to the starter terminals can lead to accidental short-circuits and fuse blows in the electrical system.
If the car starter is getting stuck then it’s probably time to replace it with a rebuilt or a new one.
If your car makes a machine gun sound under the hood when you try to start it, it may be one of several reasons – the car battery voltage is low, the battery or alternator connections are loose or corroded, or the car’s starter is faulty.
If your car starter only clicks when you try to start and fails to crank the engine, in some cases, hitting the starter may get it to start the engine.
Rebuilding or replacing it with a new one is a more reliable solution.