BMW Fuel Filling Problem

Our customer brought her BMW 440i xDrive in with a BMW Fuel Fillering Problems. Every time she would fill the fuel tank, the nozzle at the gas station would kick off every 5-10 seconds. There are many different reason why your there are issues with filling the fuel tank. Above all, these systems need to be gone through systematically. As a result, this will ensure the repair is performed correctly.

Inspection & Replacement

Collapsed hose behind fnder liner looking left from right rear wheel.

We typically look at is the EVAP charcoal canister to start. This canister filters evaporative gases from the fuel tank and fuel system. The vapors are scrubbed before being released to atmosphere. This canister is attached to multiple different system such as the fuel tank, fuel filler, and intake manifold via the purge valve. For example, on this customer’s car, the charcoal canister was wet around the fittings, so we knew there was fuel in the canister. When you over fill your fuel tank or “top it off’ all the way, this canister will sometimes fill with fuel. The fuel will vapor lock the EVAP system and will cause the fuel to back up in the filler neck causing this problem. Since e saw the wet hose connectors, we replaced the charcoal canister. After the canister was replaced, our customer was able to fill the fuel tank again.

Follow Up Inspection and Repair

A few weeks later, our customer called and said the fuel tank is not able to be filled again. Firstly, we performed a follow up inspection. Secondly, we removed all of the breather lines that attaches to the filler neck and charcoal canister. Because we were having these issues, we blew low pressure air though each line and all lines were free of clogs. Additionally, the air was able to flow through with ease. Thirdly, we  inspected the overflow / air pressure release hose that is attached to the top of the fuel tank,. This runs up to the top of the underside of the fuel filler neck. The hose was also clear. After that, we put these hoses back together. We saw the filler neck hose, looked a little strange. The hose is difficult to see with the heat shield covering the back side of the hose. Furthermore, the only way to see this clearly was with the wheel well liner removed and the underbelly panel, directly under the right rear back seat footwell. Even with a flashlight and zoomed in with a camera it was hard to see unless you are at the correct angle.

Another photo of delamination. Note bubbles that are no longer attached

Next, we removed the rear heat shield and were able to access the hose from under the BMW. Once removed we felt the inside and found the inside of the hose was delaminating. The hose thickness that BMW uses is extremely thin. Approximately 2.5mm thick. Most fuel hoses are about 5.5mm thick and are reinforced with nylon thread. The BMW hose is more than half of that and does not appear to have any nylon reinforcements.

Repairing The Hose

New hose installed with reinforcement clamp.

We found a much higher quality hose that specially made for fuel filler necks. These hoses made with a very specific hose material. The inside is lined with NBR or Nitrile Butadiene Rubber. Also, the inside has a nylon helix cord that prevents from hose from collapsing. The outside of the hose is made with polychloroprene or Neoprene. This is a highly versatile synthetic rubber invented by DuPont in 1930. This prevents the rubber from breaking down due to weather, heat, ozone, and UV.

Once installed, we could not achieve the approx. 25º bend that the OEM BMW hose has. Although, we did not let this stop us. Finally, we reinforced the center of the hose with an simple hose clamp to keep the hose from folding. Overall this was a very successful inexpensive repair.

For more information on how to get your BMW in the shop for BMW Fuel Filling Problem diagnostic, service, maintenance or custom work, contact us at 425-254-0627. You can also schedule an appointment or receive a quote by clicking here. Meister Werks European & Import is located one block south from The Renton Landing in Renton, WA, across the street from the former Boeing Store and at the westside of the Paccar / Kenworth plant.