Alex a-class

Hey,
My w176 A180 has a problem when refueling. When refueling the car, excess pressure builds up in the tank and fuel comes out of the fuel pipe.

Where do you think the problem is?
Any help would be massively appreciated.

J3NOVA

I also have the same problem on my A250, i have to go super slow to fill the tank otherwise it violently spews back out while filling! would love to know what the issue is and how to fix!

Vin_16

Hi Alex, I hope this will help. The issue you're experiencing with excess pressure building up in the fuel tank and fuel coming out of the fuel pipe during refueling could be caused by a few different factors:

1. Ventilation System: The most common reason for this problem is a fault in the fuel tank ventilation system. If the tank isn't venting properly during refueling, pressure builds up, causing fuel to overflow.
   
2. Blocked Ventilation Lines: Ventilation lines or hoses that are clogged or blocked could restrict the airflow, preventing proper ventilation of the fuel tank during refueling.
   
3. Charcoal Canister: A malfunctioning or saturated charcoal canister, which is part of the evaporative emission control (EVAP) system, can cause pressure buildup if it fails to absorb fuel vapors properly.
   
4. Check Valve Issues: Malfunctioning check valves in the fuel tank or EVAP system can hinder the release of pressure, leading to fuel overflow.
   
5. Faulty Fuel Tank Pressure Sensor: In some cases, a faulty fuel tank pressure sensor might inaccurately measure pressure, leading to improper venting.
   
6. Fuel Filler Neck or Cap: Damage or blockage in the fuel filler neck or a faulty fuel cap might disrupt the airflow, causing pressure to build up during refueling.
   

To address this issue, it's advisable to:

• Inspect Ventilation System: Check the ventilation lines, hoses, and connections for blockages, leaks, or damage.
• Check Charcoal Canister: Verify if the charcoal canister is saturated or malfunctioning. It might need cleaning or replacement.
• Examine Check Valves: Ensure check valves in the fuel tank or EVAP system are functioning correctly.
• Inspect Fuel Filler Area: Check for any damage or blockage in the fuel filler neck and confirm the fuel cap is in good condition and properly sealing.

If you're unable to identify or rectify the issue yourself, seeking assistance from a qualified mechanic or technician with experience in diagnosing fuel system problems is recommended. They can conduct a thorough inspection using diagnostic tools to pinpoint the exact cause and recommend the necessary repairs.