The Fuel System of an air-cooled Volkswagen is not a complicated System.
But, there are some Fuel Issues which continue to plague the VW Community—some of them easily resolved with a little bit of thinking and work. These are things which most of us can do ourselves.
First, rather than running to all of the forums on the subject, it’s time to sit down to consider how the Fuel System of our Beetles works.
CAUTION: When working with Gasoline—ALWAYS work outdoors and away from any source of flame or spark!
The Fuel Tank:
Complaints about Gasoline Fumes are common. Two things usually contribute to Gasoline Odor in the Trunk. This Odor often penetrates to the Cabin area.
Let’s talk about the Tank Filler Neck. Note that there is a tiny Tube coming off the Neck
pointing towards the left side of the car. By removing the Gas Cap and looking into the Filler Neck, we can see the Tube protruding into the inside of the Filler Neck. Where it protrudes, it is slightly pinched. This is to limit the amount of liquid gasoline which can escape through the Tube. A tiny Rubber Vapor Hose (N203531—ID-2.0 mm/OD-3.5 mm) is pushed onto the tube where it exits the Filler Neck. It needs no clamp since it fits tightly and there is no pressure upon it. (Note: Vapor Hose also may be marketed as Vacuum Hose.)
The Vapor Hose loops back towards the driver, then back again to the front of the car where it is pushed through an opening and allowed to dangle several inches beneath the car. Thus, any Gasoline Vapors will exit beneath the car and will not escape through the Trunk area and into the Cabin. If the Vapor Hose is missing or improperly routed—Gasoline Vapors will permeate the Trunk area and pass into the Cabin. Be sure that the Hose is present and routed through the hole to beneath the car. 2 Hose Clips (111-201-261) keep the Vapor Hose stabilized on the Cowling Loop.
If the Tank Filler Neck Tube becomes plugged, gasoline will not flow properly from the Tank Outlet. Also, make certain that the Vapor Hose is not pinched or plugged.
The Fuel Sender:
If your car has an original factory Fuel Sender, most likely the Rubber Boot on the Sender Arm has deteriorated. When the Boot deteriorates, it allows Gasoline Fumes to leak into the Trunk Compartment and to penetrate the Cabin. There is no repair to this Boot and no replacement Boots are available. It is time to replace the Sender. Replacement Senders do not have a Boot—instead, they are manufactured in a manner which does not require the Boot.
A Clean Fuel Tank:
We want a clean Fuel Tank. What goes into the Fuel Tank will continue to pass through the Fuel System and into the Carburetor. So, we must keep an eye on our Fuel Tanks. If your Beetle’s Fuel Tank has not been cleaned in years, it is time to examine its contents. Usually by removing the Fuel Sender (5 screws), and using a strong flashlight, we owners can observe any gunk which may be deposited at the low point. The low point is where the debris will clog the Tank’s Outlet. If you observe gunk plugging the Tank—it’s time for Tank removal and cleaning. This requires the removal of the Fuel. Some of us will be unable to perform this operation. Most mechanic shops can handle this procedure. When the Sender is removed, the Sender Rubber Gasket-Seal (113-919-133) should be examined for any damage.
At the time the Tank is removed and cleaned, it is imperative to observe the Outlet Strainer (111-209-147A). The Outlet Strainer is a long, skinny fine-mesh strainer of brass or copper. The Strainer is pushed up into the Tank. Gunk accumulates at the lower part of the Strainer and begins to build, with time, until it eventually can cover the entire Strainer—resulting in a stoppage at the Outlet.
Sometimes a Strainer has corroded from moisture, which also can accumulate in the Tank. New Strainers are readily available for replacing damaged Strainers.
The next thing to check is the Strainer/Outlet Retaining Nut (also called a “Nipple) on the Fuel Tank Outlet (111-298-221A). If the gasoline-resistant washer is damaged or frayed, it’s time to replace the entire Retaining Nut and Outlet Tube.
From the Fuel Tank, gasoline flows through a short length of Fuel Hose into the Metal Fuel Line, which runs the length of the inside of the Tunnel. It is necessary to have a flexible Fuel Hose between the Tank and the Metal Line to absorb vibration/movement. If the Line were rigid between the Tank and the Metal Tunnel Line, it eventually would break due to vibration fatigue.
If this flexible length of Fuel Hose is frayed or just old, it is time to replace it. Cut a new length to match the old one. You want to have enough Hose there so that when the Tank is removed, it can be lifted to provide access to the Hose and its Hose Clamps. Although the gasoline at this point is solely fed through the Line by gravity, the Clamps provide security against the loosening of the Hose between the Tank and the Metal Fuel Line.
Metal Fuel Line:
Through the Tunnel, lies the Metal Fuel Line. The Metal Line is a 6 mm Outside Diameter Metal tube. It exits the rear of the Tunnel. At both the front, where the Metal Fuel Line enters the Tunnel, and at the rear, where the Metal Fuel Line exits the Tunnel, there are Rubber Grommets to buffer the metal of the Tunnel against the Metal Line. As well, the Grommets prevent the entrance of moisture and dirt into the Tunnel where these elements can damage the various components which reside inside the Tunnel. Replace the Grommets (111-209-189A) if they are missing or damaged.
Fuel Hose to the Engine Compartment:
At the nether end of the Metal Fuel Line (where it exits the Tunnel) there will be a length of Fuel Hose. This Hose runs to the Fire Wall where it connects to a Metal Fuel Line which passes through the Firewall Tin and into the Engine Compartment. Again, the consideration is for flexibility due to vibration of the car, especially at the Engine. If the Fuel Line were rigid from the Tunnel into the Engine Compartment, it soon would weaken and rupture.
If the Flexible Fuel Hose from the Tunnel Metal Line to the Metal Line passing into the Engine Compartment is old/damaged, it’s time to replace that Hose and to secure it at both ends using Clamps.
Metal Fuel Line into the Engine Compartment:
A Metal Line passes through the Fire Wall Engine Tin. A Rubber Grommet (111-127-591) inserted into the Fire Wall Engine Tin, buffers the two metal surfaces so that the vibration of the car/engine will not cut through the Metal Fuel Line. If this Grommet is missing or damaged, it’s time to replace it with a new one.
The Metal Fuel Line which passes into the Engine Compartment is not “free-floating”. It is secured by a small Bracket (311-127-525) to the Fan Housing. It is not unusual for this Bracket to be missing altogether. I do not know if these Brackets are available in the after-market, but they can be found at salvage yards. The Bracket requires a buffering piece of rubber which surrounds the Metal Fuel Line, so that when the Bracket is secured to the Fan Housing, the Metal Bracket and Metal Fuel Line do not vibrate against one another. In the photos (below) I replaced the old, hardened Rubber Buffer by cutting a short length of Fuel Hose and slicing it lengthwise to encase the Metal Line before installing the Line into the Bracket. For illustrative purposes, I inserted only a shortened piece of Metal Fuel Line into the Bracket.
Fuel Hose In the Engine Compartment:
The Engine Compartment Metal Fuel Line ends short of the Fuel Pump. Again, at this point, a short length of Fuel Hose is inserted. The purpose is the same as at other locations—to prevent damage that would occur should the Metal Line be rigid.
The Fuel Pump is the transfer station, if you would, which pressurizes the gravity-fed gasoline to the Carburetor.
From the Outlet of the Fuel Pump to the Inlet of the Carburetor there also is a section of flexible Fuel Hose.
This completes the journey of gasoline from the Tank to the Intake and Combustion System for the Engine.
Maintaining Clean Fuel to the Combustion System:
During the 1980s, I found it necessary to install Filters into our VWs due to the advent of Ethanol which began to be added to automotive fuels. Ethanol readily combines with water. The air contains moisture. Our vintage Volkswagens do not have a Sealed Fuel System. Each time we remove the Gas Tank Cap, we allow air (i.e. moisture) to enter the Tank. Ethanol combines with this accumulated moisture and carries it through the Fuel System—right into the carburetor. IF—if we don’t install a Fuel Filter at some point. The Ethanol also causes damage to the inner core of the Fuel Hoses. Particles begin to break loose and can enter both the Fuel Pump and the Carburetor. These particles contribute to plugging the flow of Gasoline through both the Pump and the Carburetor. As well, moisture in the Tank and Metal Lines results in oxidation—if you’ve ever opened a Carburetor, you probably have seen the resultant fine, red sediment.
As you know, 1967beetle.com advocates the installation of a Fuel Filtering Device either at the outlet of the Gas Tank or at the rear of the car before the Fuel Line enters the Engine Compartment. Once installed, the Fuel Filter must be monitored regularly– especially if your Gas Tank has not been recently cleaned. Create a Maintenance Schedule Sheet that includes the Monitoring of the Fuel Filter.
Understanding the Fuel System of your Beetle will help you to diagnose future problems. When you have what appears to be a fuel problem…mentally trace the System rather than to play a guessing game. Knowledge is power—use it wisely!
I want to thank David Brown of Pennsylvania for supplying missing VW Part Numbers. We are fortunate to have Volkswagen Trained individuals like David who are willing to spend time working with us to enlarge our understanding of our Vintage ’67 Beetles! David has a 1967 Standard-Standard Beetle–which I keep encouraging him to restore. Maybe we will say something in the future about what is a “Standard-Standard” Beetle.
Neva Salser contributed to this Article through her photographic skills. Thank you, Neva!