Mercedes Benz Vapor Canister Purge Solenoid Troubleshooting Guide

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The canister purge valve is an important part of the Mercedes-Benz vehicles' Evaporative Emission Control (EVAP) system because it prevents fuel vapours from escaping into the atmosphere by catching and keeping them in a charcoal canister.

The EVAP system permits these vapours to be discharged into the motor when it starts operating at a regular speed, where they are burned like ordinary fuel. The canister purge valve in your Mercedes-Benz regulates vapour flow, deciding when and how much vapour enters your vehicle's powertrain.

The purge valve in modern Mercedes-Benz is an electronically powered solenoid controlled by the engine computer. The valve is closed when the engine is turned off. Once your engine is running, the computer opens the purge valve slowly and steadily. This motion permits fuel vapour from the charcoal canister to reach the engine and be burned.

The EVAP system is made up of all of these pieces connected by a hose. Dust and debris, like many other car components, can block the canister. The purge valve can potentially shatter due to extreme environmental conditions. If the purge valve breaks, it might cause issues with the EVAP system, lowering the emission output level of Mercedes-Benz vehicles.

Table of Contents

  1. What Does the Canister Purge Valve Do?
  2. What Happens When the Canister Purge Solenoid Goes Bad?
  3. What Are the Symptoms of a Faulty Purge Valve?
  4. How Is the Solenoid (Purge Valve) Tested for Mercedes Benz?
  5. Conclusion

1. What Does the Canister Purge Valve Do?

Vapour canister purge valve

Because the canister can only retain so much gas vapour, it catches the vapours from the gas tank and temporarily stores them in the charcoal canister until the engine is running under particular conditions.

The trapped gas vapours in the canister will be expelled and burned inside the engine. This is done by the vapour canister purge valve, which also accurately controls the amount of gas vapour expelled from the gas canister.

The vapour canister purge valve is the component that opens and closes the passage between the gas tank's vapour lines and the intake manifold. It works like a switch, allowing gas vapours to be pumped into the air intake when it opens and stopping when it closes.

Canister purge solenoid

The vapour canister purge valve in modern Mercedes-Benz cars is an electronically actuated solenoid that is controlled by the engine computer. When the engine is turned off, the purge valve is closed; when the engine is turned on, the engine computer progressively opens the vapour canister purge valve, allowing a set amount of gas vapours to escape and be burned in the engine.

When no electricity is supplied to the solenoid, the valve remains closed; however, when a voltage is applied, the valve opens, allowing the purge valve to release gas vapours into the engine. If the solenoid develops faults and ceases to function properly, it will be unable to open or close, causing a slew of troubles.

Purge valve

Many modern Mercedes-Benz cars contain power control modules, or PCMs, that only allow the gas vapours to be released while the vehicle is moving at a constant speed, usually in higher gears. This is because when gas vapours are emitted when the automobile is travelling at a low speed or under load, they might change the air-to-fuel ratio, causing misfires in the engine.

2. What Happens When the Canister Purge Solenoid Goes Bad?

A vacuum leak can occur if the vapour canister purge valve becomes weakened. This will have a direct impact on the idle speed and quality of the engine. The vapour canister purge valve may also fail and become stuck open or closed, or become clogged, preventing the gas vapours from being discharged.

Location of purge valve

There are other times when gas vapours are emitted at an inopportune time. This can result in an improper air-to-fuel ratio, which can lead to a variety of problems. To regulate the proper flow of gas vapours, the vapour canister purge valve should always open and close at the correct times.

Modern Mercedes-Benz cars with a solenoid that controls most of the purge valves may experience problems with the solenoid over time, causing the vapour canister purge valve emission system to fail. When the vapour canister control solenoid fails, it can cause a variety of issue codes to appear, which can be difficult to diagnose and repair.

Purge solenoid

P0440 or Evaporative Emission Control System Malfunction, P0441 or Evaporative Emission Control System Incorrect Purge Flow, P0443 or Evaporative Emission Control System Purge Control Valve Circuit, P0444 or Evaporative Emission Control System Purge Control Valve Circuit Open, and P0445 or Evaporative Emission Control System Purge Control Valve Circuit Shorted are the trouble codes that can be triggered by a bad vapour canister purge valve.

3. What Are the Symptoms of a Faulty Purge Valve?

When the purge solenoid fails, it causes issues with the EVAP system, which has an impact on the vehicle's emissions output. A malfunctioning purge solenoid will usually exhibit any of the five symptoms listed below, alerting the driver to a potential problem that requires attention.

Purge valve installation

Mercedes Benz Experiences Rough Idling

A rough idle is one of the first signs of a malfunctioning canister purge valve. You will notice the automobile running irregularly while stopped or moving at moderate speeds in this situation. A vacuum leak will result if the canister purge valve fails and sticks open, affecting the engine idle speed and quality.

A broken or damaged purge solenoid, or any of the hoses connected to it, might also create a vacuum leak. It must be addressed as quickly as possible, since it may cause your engine to completely stall.

Purge solenoid connector

Engine Performance Problems With Mercedes Benz

A car with a failed EVAP canister purge valve will show indicators of poor engine performance in addition to a rough idle. It's possible that the engine will feel "weak" and won't create enough power for acceleration.

Accelerating will feel like you're stomping on the gas pedal and slowing down. The slow acceleration induced by the disturbed combustion process caused by the failed purge solenoid must be rectified immediately for repairs.

Vapour purge solenoid

Difficulty in Getting Started With Mercedes Benz

Difficulty starting the automobile is another common sign of a faulty vapour canister purge solenoid. Again, if there is a vacuum leak as a result of a problem with the canister purge solenoid, the vehicle may have trouble starting reliably.

A vacuum leak allows unmetered outside air into the engine, causing the air-fuel ratio to be disrupted and performance concerns as a result of the internal combustion process being interrupted. The engine may eventually refuse to start totally.

Purge solenoid location

The Check Engine Light in Mercedes Benz Is Turned On

The Check Engine Light could potentially be caused by a faulty canister purge solenoid. If the computer identifies a problem with the purge solenoid circuit or signal, the Check Engine Light will illuminate, alerting the driver to the problem.

A Check Engine Light can be caused by a variety of other issues, so having the vehicle checked for trouble codes is recommended to be sure.

Low Fuel Efficiency With Mercedes Benz


Another indicator of a failed canister purge valve is a poor gas mileage. Instead of being burned, the fuel vapours in your car will be evacuated through the EVAP canister.

Instead of reaching the combustion chamber, gasoline is consumed before it can start the process of combustion. This means that your car will waste gasoline rather than use it efficiently.

The canister purge solenoid is an emissions component and so plays a critical role in ensuring that the vehicle complies with emission regulations. The purge valve keeps harmful hydrocarbons from spilling out of your exhaust.

Purge solenoid

As a result, if you suspect a problem with your canister purge solenoid, get the Mercedes-Benz car diagnosed by a professional technician to see if the canister purge solenoid or vacuum hose needs to be replaced.

4. How Is the Solenoid (Purge Valve) Tested for Mercedes Benz?

The right process for testing the purge valve can be found in the Mercedes-Benz service manual. The technique may vary based on the brand and model of the Mercedes-Benz vehicles.

The purge valve in most cars is generally closed, which means it should be closed when there is no voltage and open when there is.

The service handbook for Mercedes Benz, for example, suggests applying battery voltage to the purge valve terminals and listening for an audible click. To demonstrate, you can use a 9-volt battery. There is an audible click from this purge valve.

Testing purge solenoid

According to the service manual for Mercedes Benz, the next step is to see if the purge valve closes properly and does not leak. You can connect a hand-held vacuum pump to the purge valve and apply vacuum.

Testing purge solenoid

The vacuum is rapidly dissipated. This purge valve is leaking and needs to be replaced. On the dashboard, there should be a "Check Engine" light. It must be scanned, and you are likely to get the code P0446 - Evaporative Emission Control System Vent Control Circuit Malfunction - should be returned.

Testing purge solenoid

An investigation into the EVAP system should discover a gradual leak. Now you know the root cause of the problem

You can also put a purge valve from a different car to the test to show the difference. It should maintain a strong vacuum for a long time, even after one minute.

Testing purge solenoid

The battery voltage should now be connected. The vacuum should drop as soon as the purge valve clicks. This shows that the purge valve performs well and is not faulty.

Testing purge solenoid

EVAP-related Check engine light codes are frequently produced by a defective vent valve or gas cap, in addition to a purge valve.

5. Conclusion

Together with the car's EVAP system, the vapour canister purge valve ensures that less harmful pollutants are emitted into the environment. If you see any indicators of a faulty vapour canister purge valve, have it checked and fixed right away, not only to maintain your vehicle in good working order but also to help the environment.