The firing up valve is used when the car is initially steamed up.  After the pilot is lit the burner vaporizer is usually too cold for vaporization of the kerosene the burner normally uses.  The burner forks are heated with the torch while heating the pilot vaporizer.  Once the pilot is lit and has burned for a few minutes the firing up valve is opened to permit the easy to vaporize pilot fuel to the burner.  As the pilot fuel vaporizes easy it allows the cold burner to ignite quickly with little danger of a burner backfire.  The firing up valve is left open for a few minutes to insure the burner vaporizer is good and hot and then it is closed and the burner fuel valve opened to admit kerosene to the burner so that steam can be generated.

The second use for the firing up valve is to relight the burner after the car has been sitting for a while.  When a Stanley car has been sitting for a period of time (typically anything longer than 15 to 20 minutes) with the burner shut down the vaporizer tube will cool.  If the burner valve is opened to relight the burner the liquid fuel hits the vaporizer and cools it even more.  Liquid fuel ends up being discharged from the burner nozzles into the mixing tubes where it lays. When enough vapors are emitted that the pilot can light them the burner backfires and burning of the raw fuel happens in the mixing tubes.  Just as was done when the car was initially fired up, the firing up valve is first opened for a short period of time to light the burner and heat the vaporizer prior to the burner valve being opened for kerosene to be burned.

The firing up valve provides a connection to the pilot fuel tank and it’s easier to vaporize gasoline (or today Coleman Stove Fuel or Hexane). If the burner has been off for a period of time the firing up valve is quickly opened for a second or two to provide a shot of pilot fuel to the burner vaporizer. As the pilot fuel is easily vaporized most of the liquid will vaporize and thus the burner has a better change to light properly and not backfire. Depending on how long the burner has been shut down, the firing up valve can be opened several more times or left open for a minute or so to insure the burner vaporizer is hot before the main burner valve is opened to allow kerosene to fuel the burner.

One thing the Stanley driver must pay attention to when operating the firing up valve and the burner valve is that both valves are never opened at the same time. A quick examination of the piping diagram reveals that the firing up valve and the burner valve both share common piping between each valve and the burner. This means that should the firing up valve be open or even partially open when the burner valve is opened, the higher-pressure fuel from the burner fuel system will flow into the lower pressure fuel of the pilot burner fuel system. The result will be a building of pressure in the pilot fuel system above it’s normal 25 to 30 PSIG operating pressure. The pilot will start to burn a more vigorously with the increased pressure and there is the chance the pilot fuel tank or some of the pilot fuel system piping could rupture or leak and spray fuel that could ignite.

Additionally the pilot fuel will become contaminated with kerosene making it much more difficult to vaporize. Since the pilot burner’s vaporizer is designed for the easily vaporized pilot fuel (its only a few inches long and not the nearly 8 feet long like the burner vaporizer), when the kerosene contaminated pilot fuel reaches the vaporizer it will not be heated into a gas but will end up being discharged from the pilot nozzles into the pilot mixing tube. In a short amount of time the pilot burner will backfire due to being flooded with liquid kerosene.