Engine fires are common in ACVW's.
I had a friend who was a fireman that said he had been called to a number of fires involving VW's. Their standard procedure when driving up to one was to isolate the area, and protect other property around the fire.
You see, the stock type I VW case is not pure aluminum. It is an alloy which includes aluminum and magnesium. The magnesium is what is burning. And water won't put it out.
The vast majority of VW engine fires are caused by problems with the stock fuel line going from the fuel pump to the carb.
Two things happen.
1. The line deteriorates inside the fabric weaving and
leaks gasoline onto the engine.
2. The brass fitting on the carb comes out.
This is the only fuel line on a VW that has pressurized fuel in it. The line from the other side of the fuel pump to the front of the car and the gas tank is gravity fed. If either of these problems occur, the engine may still be running with the fuel that is already inside the carb. So, fuel literally SPRAYS inside the engine compartment. Additionally, most of our beloved ACVW engines are often covered with a coat of oil soaked dirt.
Since this area is nice and warm, the liquid gasoline evaporates rapidly creating a fuel air mixture that is easily ignited by any convenient spark. Like the ones on the brushes of the generator. Result, fire in the engine compartment. If it gets hot enough, the magnesium starts burning and, well, you know the rest.
The best prevention is proper maintenance. Replace
all fuel hoses and put hose clamps on them. If you are running a
stock type carb, the best fix is to remove the brass tube and use a 1/4-20
die to put threads on it. Then, run a 1/4-20 tap into the opening of the
carb
body and screw the tube back in using a drop of locktite
on it. At minimum, wrap a piece of wire around the neck of the carb and
the hose clamp on the fuel inlet tube.
Another area that is prone to produce a leak is the metal tube that passes thru the front engine tin. There is supposed to be a rubber grommet that prevents the steel tube from rubbing on the sheet metal. The rubber deteriorates, The metal tube rubs on the sheet metal and soon there is a hole worn in the tube.
I found a nice fix for this, go to a hardware store that sells parts to repair electric lamps. You can buy a kit of parts that includes tubing that is threaded on the outside. The kit will also include nuts that fit the threads. Use a 1 inch tube on the hole in the sheet metal and put a nut on either end to hold it in place. The metal fuel tube fits perfectly inside.
Finally, please, a hundred times, please don't use plastic fuel filters on the pressurized line between the fuel pump and the carb.
If there is a fire, the plastic melts very quickly and
the fuel in the filter simply feeds the fire.
Alternate places to put the filter:
1. At the bottom of the fuel tank. There
is a hose that goes from the tank to the steel fuel line that runs inside
the chassis.
2. Under the car just in front of the axle, where the
steel fuel line comes out of the chassis. There is a hose there that
goes to the metal tube that runs to the fuel pump.
You do carry a fire extinguisher, don't you?
One of the things I found interesting is that most VW shows REQUIRE that all cars entered for judging have a fire extinguisher. (See, they already know this stuff).
So, what kind should you have? There are some sold
by automotive high performance shops that still have halon or some similar
chemical. These are nice because the powder in standard home type units
is extremely corrosive. However the cost is high.
Often over $50.
So, most folks end up with a standard home/kitchen type. I have had two engine fires, both caused by the brass fitting coming out of the carb. Both times, I was able to use the extinguisher I had with me to get to the fire and put it out before the magnesium in the block caught.
In many cases, you can save the car. You may need some paint touch up work under the rear window, and replacement of all the wiring in the engine compartment, but atleast you can save the car. The main thing is to not lose your head. You can raise the engine lid and spray the fire with the extingusher within 15 seconds. Trust me, I know. Practice in your drive way. It's cheap insurance.