Some fires may be beyond our control, but we can do a lot to reduce the chances of a busbeque. Good quality fuel lines are only one step. A second step involves correcting a weakness in the fuel system found in our older VWs. This system relies on gravity to feed the engine fuel. Gravity is a fantastic force with which to do work both effectively and cheaply. Continuous, reliable, free, and not prone to mechanical failure, it is no surprise gravity is used in a wide variety of tasks, from public water systems to electricity generation. In this case, gravity’s job is to pull fuel out of the tank via an outlet tapped into the tank’s underbelly. From there, the gas follows a few feet of rubber fuel hose, to a metal fuel line passing into the engine compartment, and then travels another foot or so through more rubber hose to the fuel pump. The pump then applies the correct pressure to send gas along to the carburetor(s) or fuel injectors. The drawback to using an open gravity feed mechanism is that it cannot be turned off. In the event a leak occurs, fuel will continue to flow unabated, despite turning off the engine, making it even more difficult to extinguish fires once they start. Even if the initial blaze is quelled, the continuous stream of fuel from ruptured or melted fuel lines makes re-ignition highly likely.
(As an aside, the metal line mentioned above should pass through a rubber grommet installed in the front engine tin. If this grommet is missing or in poor condition, engine vibration may cause the tin to cut through the line leading to gas dripping directly on to the heat exchanger or into the engine compartment. Keep this grommet in good health!!)
One of the more popular resolutions for the gravity issue involves installing a fuel cutoff valve to block the flow of fuel. For bugs, Type IIIs, and other VWs with gas tanks located up front, some owners install manual valves, which need to be actuated by hand, near the tank. Of course in a bus, with the tank in the rear, this is a little more inconvenient as one must crawl under the bus to close a valve located near the tank. In the event of a fire emergency, one can expect to get close and personal with the flames to actuate the valve. I have seen some setups with manual valves rigged to cable systems that enable the driver to work the valve from the cab or some other relatively safe place, but this seems like a complicated solution since easily installed electric valves are readily available. Bottom line is that either valve will stop the flow of fuel if a line ruptures (not to mention making it much easier to replace fuel system components down stream from the valve).
After reading about the options and contemplating the ease of use and degree of installation difficulty, I decided it was worth the time and money to put a 12-volt fuel shutoff valve in Moby. By far, the most popular model is the AFC-121 (it also has an optional reusable fuel filter). The AFC-121 works by letting fuel flow when power is on and blocking it when off. The default position is off so in the event of a malfunction or electrical issue, they are pretty safe. A bypass line can be installed to preempt failure, but in my opinion this leaves the same fire hazard that we are trying to eliminate. If there is a valve issue, a bypass can easily be installed at that time.
One of the reasons I purchased the AFC-121 is its flexibility in terms of installation. They can be located very close to the tank outlet or replace it all together. The wiring can be hooked up to the ignition system and activated when starting the engine or deactivating when turning the car off. Or, if you would rather, they can be wired independently and turned off/on at will in the event of fire or to thwart thieves. Before the valve arrived, I planned on following the method of installation shown in this thread and mount the valve directly to the tank outlet, eliminating the chance of uncontrolled leaky fuel lines. However, after delivery, I agreed with some of the posters on the above thread that the AFC-121’s weight might be too much for the connecting components. I crawled under the bus to reconnoiter a place for a mounting bracket to support the valve in this type of setup, but I did not see a suitable location (though the one I eventually used might be made to work). Instead, I decided to mount the AFC-121 near the outlet, and connect it to the tank with a very short piece of rubber fuel line. One note: this short rubber hose could be replaced with a hard metal line; I might try to do so at a later date.
If needed, click on the pictures below to make them larger.
Edit: Additional Samba Thread
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The AFC-121 12-volt fuel shutoff valve. I also purchased the fuel filter but found that space was very limited at my chosen mounting location and did not install the filter. I installed the valve at the same time I switched all the fuel lines to 30R14 Barricade hose. To make this project easier, safer, and cleaner DRAIN THE FUEL TANK FIRST!
In most threads I read, owners installed the brackets using holes drilled into the bus frame. I do my best to complete projects without modifying, drilling, or cutting my cars, and selected the seat belt reinforcement bolt on the left as the place to mount the bracket. I will mention that this area lacks working room and the job would be a lot easier if the heat exchanger tube (black, ribbed object in lower right corner), engine, and trans were out. Adding metal lines or a more complex bracket for a tank mounted valve would almost require their removal.
I wanted a bracket material fairly easy to work with since I did not know how many attempts this project would require. I selected a 1-inch wide x 36-inches long x 1/8-inch thick aluminum strip. May not be the best option in terms of longevity, but it currently works great. Now that I know what needs to be done to make a bracket, I will use steel in the future because it is less prone to fatigue at any bends.
The bracket is 3 7/8-inches long in total. I came up with that measurement by determining what was needed at the mounting area and then providing a section to support the valve. Looking at it now, I just should have made the support section an 1/8-inch longer for an even 4-inches!! Oh well. The mounting section needs to fit in the seat belt reinforcement plate and measures 1 3/8-inches from the end of the strip, while the support section is 2 1/2-inches as measured from the line that divides the two regions.
I must apologize for the photo quality, the camera was on its last legs. This photo shows the bracket cut from the strip. The hole for the seat belt reinforcement bolt needs to be placed in the center of the mounting section, 11/16-inches from the dividing line and 1/2-inch from the edges. I used a punch to dimple the spot and provide a biting surface for the drill bit.
3/16-inch pilot hole drilled for seat belt reinforcement bolt hole.
Pilot hole widened to 25/64-inches; just big enough for the bolt. For strength, I wanted to preserve as much metal around the hole as possible.
The mounting site is not perpendicular to the ground. In order for the valve to hang vertically (I do not think it matters much for valve function, it’s purely aesthetic here), the bracket needs to be bent along the dividing line. One vice + one hammer = bent aluminum.
Final bend should be 50 degrees. It’s not quite ready in the photo.
3/4 of an inch from the bend and 1/2-inch from the edges, I dimpled the location for the valve holder bolt.
The valve holder bolt hole was drilled to 15/64″ after first drilling the pilot hole.
As we’ll see in a later photo, the valve holder relies on tension. Not confident that tension would work successfully against the unrelenting, ever present, force of gravity over time, I decided to add a back-up retainer in the form of an electric zip-tie. 1-13/16″ down from the bend and 1/4″ from the edges, I drilled two 3/16″ holes through which the zip-tie will pass and secure the valve between it’s upper and lower sections.
To fasten the valve to the bracket, I used a 1 1/4″ electrical conduit pipe clamp. It fit perfectly around the valve top and, and with the retaining bolt tightened, seemed quite adequate to keep the valve from slipping. Since the AFC-121 is fairly heavy for its size, I worried about it slipping over time due to vibrations from driving; hence the zip-tie mentioned earlier.
Assembly mock-up. Note: the valve did not end up in this orientation, I was just testing fit.
Bracket mounted to the seat belt reinforcement plate. Front of the bus is to the left, fuel tank outlet is barely visible just to the rear of the bracket. The AFC-121 will go on the bracket side that faces front so as to provide space between the fuel line connections and heat exchanger tube.
Valve holder in place, bolted to the bracket with a 10 mm bolt from the parts bin.
Two 1/4″ barbs with 1/4″ threads (not supplied with the valve) are required to hook the fuels lines to the valve. I tried a 3/16″ barb but for some reason I could not get a solid, tight seal with my 3/16″ fuel hose. I sealed the threads with yellow, fuel resistant Teflon thread tape as recommended on a few forums.
Both barbs installed.
Since the mounting space was limited, I decided to hook up the fuel lines and wire leads before I installed the valve. An inlet (left hose above) is labeled ‘IN” on the valve, the other hose is the outlet. For the wiring, I did not want to permanently hard wire the valve because I am pretty sure it will need to come out to replace the fuel lines and possibly fuel filter. Therefore, I wired an extension (red) to the hot lead with a heat shrink wrapped butt connector and put a spade connection (not visible in the photo) on the other end to connect with power from the bus. Speaking of power, there are a few options for a power source: the starter, battery, or separate hot line from an independent switch. It all depends on when you want the valve on/off and how much control you need. I connected ground or earth (black) at the same location as the transmission ground-strap.
Everything installed; hose clamps were added at the junctions later. After a little less than a thousand miles, the bracket and clamp are holding nicely.