THE POWER FUEL PUMP LOCATED IN THE PUMP BOX UNDER THE FRONT FOOT BOARDS

Stanley cars always used a pressurized fuel system for the burner.  Pressurization was achieved by the a piston powered pump supplying fuel to a pair of pressure tanks often referred to as service tanks.  A cushion of air in the tanks served as an elastic medium for the fuel to be pumped against and thus pressurization of the fuel system achieved.  A piston pump, powered from the engine crosshead on non-condensing Stanley cars and from the rear axle for condensing Stanley cars, was used to draw fuel from the fuel tank and supply it to the pressure tanks.

HOW THE POWER FUEL PUMP WORKS

The fuel pump only operates when the car is in motion as it is powered off the rear axle of the car for later Stanley models like the Model 735 or driven from the engine crosshead for early Stanleys.  The fuel pump will pump fuel to pressures well above the 140 PSIG setting of the fuel automatic and provides a volume of fuel sufficient to quickly replenish what is used from the pressure tanks while the car is stopped at a light.

The cars manufactured up through 1914 placed the pump under the driver's foot board.  The fuel pump, like the water pumps were of a "short stroke" design.  Driven from the right-hand crosshead wrist pin of the engine, a rocker arm arrangement reduced the 4" engine stroke to the required 1-1/4" stroke of the pump's piston.

In 1915 Stanley introduced the "long stroke pumps" which ran at a much slower speed and were a lot quieter than the short stroke pumps.  The long stroke fuel pump has a 4" stroke and uses a larger diameter piston than its short stroke cousin.  The pumping action relies on check valves similar to that of the water and oil pumps.  The check valve balls were 3/8" diameter.  Mounted on the right rear axle is the pump drive box.  The pump drive box provides gearing and a crank arm to drive the power pumps.  At the end of the crank arm the pump drive rod is attached.  The result is that the pumps operate at a much slower speed as a result of this design making them quieter (see the photo and discussion at the end of the power water pumps article for additional information).

The Stanley power fuel pump on a condensing Stanley operates identical to the power water and oil pumps.  As the piston is drawn out of the cylinder a vacuum is created which draws fuel from the supply tank to fill the volume within the cylinder that the piston occupied.  The fuel is drawn from the fuel supply line and the fuel tank into the pump through the suction check valve while the delivery check valve keeps oil from being drawn in from the delivery piping.  Actually with 140 PSIG pressure on the delivery side of the pump, if the pump's delivery check valve is not functioning properly the pump usually will not pump fuel.

As the piston is pushed back into the cylinder the fuel that has been drawn in now tries to run back out of the cylinder through the suction check valve that was open.  This action forces the suction check valve to close and pressure begins to build on the fuel in the cylinder as the piston continues its motion into the cylinder.  When the pressure within the cylinder becomes greater than the fuel pressure of the delivery piping after the pump, the delivery check valve opens allowing the fuel just drawn into the pump's cylinder to escape and flow into the delivery piping.  Once the piston is fully inserted in the cylinder no more fuel is supplied by the pump to the delivery piping and the cycle starts over with the piston being pulled out of the cylinder to draw in more fuel.

The power fuel pump in a Stanley is located below or at least at the same level as the fuel supply tank.  This affords an easy way for it to be initially primed with fuel.  Rings of graphite impregnated packing are used at the end of the cylinder to for a seal between the cylinder and moving piston.  Maintenance is generally required every couple hundred miles to snug up on the packing nut.  There is no adjustment for the amount of fuel pumped.