Causes for a Mercedes not to start (Top 7)

In this brief guide, we are going to provide you with the causes for a Mercedes not to start and what you can do to rectify these causes before they affect your car.

There are a number of causes that can make a Mercedes not start. In this blog, we’ll go through the most common causes that a Mercedes driver may encounter.

What causes Mercedes not to start?

Most of the common causes for a Mercedes to not start are:

  • Low battery voltage
  • Damaged fuses or relays in the starter circuit
  • Gear selector mode failure
  • Brake light switch failure
  • Low fuel pressure 
  • Starter motor failure
  • Damage to the ignition system, spark plugs and switch
  • Crankshaft position sensor failure
  • ECM/PCM computer failure
  • Driver authorization system failure

Why does Low battery voltage cause a Mercedes not to start?

The starter motor needs a specific amount of voltage to function properly. If it is not getting the desired amount of voltage from the battery then it will not work and ultimately the engine won’t start.

Which errors are shown as a result of this cause?

The battery light is switched on, on the dashboard indicating a sufficient charge in the battery to start the engine.    

How to fix this Mercedes problem?

If the battery is too old then replacing the battery may be the best possible solution or else charging the battery from an external source till it has sufficient voltage is the solution.

Why do Damage fuses or relays in the starter circuit cause a Mercedes not to start?

Fuses and relays control the current and if they are damaged then the circuit is not complete and the starter motor does not receive a current to start. These devices get burned when too much current flows through them to avoid further failure of other systems.

Which errors are shown as a result of this cause?

No specific error is shown if a fuse or relay is blown but you can check its state by using a digital multimeter. 

How to fix this Mercedes problem?

These are generally very inexpensive parts and the only solution is to replace them with the same ampere capacity or else they could blow again and damage other systems in the car. 

Why does Gear selector mode failure cause a Mercedes not to start?

Because you need the gear selector module to drive the car, hence if the entire module is not working then the car won’t start.

Which errors are shown as a result of this cause?

No specific error is shown but, on the dashboard, when you move the gear lever, it should change the letters from P to N and to R. If the lights do not change then the module is not working.

How to fix this Mercedes problem?

If the gear selector is defective or the cables connected to the modules are faulty then changing the entire subassembly might be an option to solve this issue.

Why does Brake light switch failure cause a Mercedes not to start?

The control unit of the car won’t allow starting the car if the brake light switch is not working. This is a precautionary measure and it requires the brake lights to be working.

Which sign is shown as a result of this cause? 

If on the dashboard, you do not see the start light on then it means the brake light switch is not working.

How to fix this Mercedes problem?

Replacing these switches is the only way to fix this problem as these are electrical devices and are very inexpensive. Therefore, repairing them is not worth it.

Why does Low fuel pressure cause a Mercedes not to start?

The engine requires appropriate fuel pressure to start and function properly. If it does not get the required fuel pressure then it’ll not start.

Which errors are shown as a result of this cause?

Not specific errors are shown on the dashboard for this cause but you might be able to diagnose the error by using a fuel pressure gauge to check the pressure.  

How to fix this Mercedes problem?

There are a number of reasons for getting low fuel pressure and repair is the most common solution. Sometimes the fuel filter is clogged or the fuel pump is malfunctioning or else the fuel lines are faulty.

Why does Starter motor failure cause a Mercedes not to start?

The Mercedes engine requires the starter motor to start itself. If the starter has failed then the engine won’t start.

Which sign is shown as a result of this cause?

The dashboard will give you the signal that the car is not ready to start if the starter motor is not working.

How to fix this Mercedes problem?

Many times the starter motor does not fail but the fuse connected to it is blown. Simply changing the fuse may solve the problem. Also, sometimes hitting the motor with a rubber hammer might work. 

Why does damage to the ignition system, spark plugs, and switch cause a Mercedes not to start?

Because the ignition system actually ignites the fuel within the engine to make it start. If this system is not working then the engine just won’t work.

Which errors are shown as a result of this cause?

A number of errors can be detected by the use of an engine scanning tool to read the actual error codes and pinpoint where the problem lies.

How to fix this Mercedes problem?

Also, in this case, most of the time the fuse is blown within the system causing the starting problem. Checking and if required changing the fuses and spark plugs or switches will solve this problem.

Why does a Crankshaft position sensor failure cause a Mercedes not to start?

Because this sensor communicates to the ECU the current position of the crankshaft. If the sensor is not working the failsafe system prevents the vehicle from starting.

Which errors are shown as a result of this cause?

Firstly, the check engine light is switched on, on the dashboard which will indicate there is a problem with the engine. Also, the car hesitates while starting if there is a problem with this system.

How to fix this Mercedes problem?

This sensor is quite inexpensive and changing it will solve the problem immediately. 

Why does ECM/PCM computer failure cause a Mercedes not to start?

Because this is the computer that controls the engine and powertrain functions as well as monitors these functions. If the computer has failed then the car just won’t work at all. 

Which errors are shown as a result of this cause?

P0606 code is the diagnostic code that the scanning tool will give if you run it on your Mercedes whose ECM/PCM has failed.

How to fix this Mercedes problem?

Changing or resetting the entire computer will solve the problem as this is one of the most important parts of the vehicle.

Why does Driver authorization system failure cause a Mercedes not to start?

Because the driver authorization system ensures the verification of the key to start the car. If this system has failed then the car is unable to start   

Which sign is shown as a result of this cause?

The dashboard will not give the start signal if the driver authorization system is not working. Generally, the low battery charge is the reason behind this system failure.

How to fix this Mercedes problem?

This system is quite expensive and repairing it from a professional might be a solution to this problem.

How to diagnose these common Mercedes start problems?

To properly diagnose these problems, you need a scan tool to read these codes from the Engine Control Unit. Firstly, if a Mercedes is not starting, it immediately informs the driver with an error message on the dashboard of some kind, or else the problem can be felt while starting.

How to prevent these malfunctions in the first place?

Regularly checking your battery health and other starting systems may save you a lot of trouble and money in the future. Although many experts suggest different number miles for battery charging or replacing, your car manual will give you a proper recommendation when you should change it.

FAQs: What causes Mercedes not to start

What would cause a car to randomly not start?

it’s usually caused by a dying or dead battery, loose or corroded connection cables, a bad alternator, or an issue with the starter when your vehicle won’t start. It can be difficult to determine if you’re dealing with a battery or an alternator problem.

How do you fix a Mercedes that won’t start?

Trickle charge your battery by using a 12-volt trickle charger if you have a relatively new battery and even though the engine won’t start. The fuse on your starter circuit, Ignition, EIS, or Fuel Pump can be checked next if the battery is not the issue.

Conclusion

In this brief guide, we have provided you with the causes for a Mercedes not to start and what you can do to rectify these causes before they affect your car.

If you have any questions or comments please let us know.

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