the burner fuel pressure relief valve and check valve is located under the right front seat at the rear of the pump box

The burner fuel system operates at 140 PSIG. This  pressure is generated and maintained by the power fuel pump as well as the hand fuel pump.  In order to perform maintenance on either pump (such as add a round of packing) the pressure must be relieved from the system.  The fuel burner fuel system's pressure relief valve provides a means for relieving the system pressure prior to performing any maintenance.  This valve is normally closed and only opened when the pressure on the fuel pressure tanks needs to be reduced.

Associated with and physically connected to the fuel pressure relief valve is a ball-check valve.  This check valve serves to isolate the fuel pressure tanks from the pumps and fuel pressure automatic.  When the car is not moving, and provided there are no leaks in the pressure side of the fuel system, this check valve does not allow fuel pressure to be present on either the hand or the power pumps or the fuel pressure automatic.  While there is a check valve on the power fuel pump (provided it is not leaking) to keep fuel pressure tank pressure (generally 140 PSIG) off the two fuel pumps when the car is not moving, the fuel pressure relief valve check valve keeps pressure off the diaphragm of the fuel pressure automatic (which can leak with an occasional speck of debris under the valve seat).

The burner fuel pressure relief valve can be used if the pressure tanks need to have the charge of air increased in the tanks. This can be accomplished by opening the fuel pressure relief valve to drop the system pressure to 30 or 40 PSIG. Air can be added through the air pressure valves to return the burner fuel system pressure to 80 to 90 PSIG. The hand pump can then be used to pump fuel and raise the burner fuel system to its operating range of 130 to 140 PSIG.

VARIOUS VALVE STYLES FOUND ON STANLEY STEAM CARS

The above photo shows an assortment of Stanley valves.  Perhaps the most common of the Stanley valves is the style shown as A-3.  This style valve consists of a brass base (A-1) which comes in a number of port configurations.  The valve stem (A-2) screws into the valve base and the packing nut shown on the valve stem tightens onto the valve base to seal the valve.  For this style valve 1/8" square graphite impregnated packing is pushed into the packing nut between the walls of the packing nut and the valve stem.  Generally only two rounds of packing can be placed in the nut.  As the packing nut is tightened down the packing is compressed to seal against the shaft and keep the valve from leaking at the stem.

An alternate valve style is shown at B.  This style valve was larger than the valve style just discussed and included a packing stuffing box as part of the valve body.  A close examination of the two valves C-1 and C-2 show the packing stuffing box without packing (C-1) and with packing (C-2).  You'll also note the packing gland on the valve stem just below the packing nut.  With the valve stem installed in the valve body two rounds of 1/8" square graphite impregnated packing is placed in the stuffing box.  The packing gland is pushed down into the stuffing box and the packing nut tightened to compress the packing against the valve stem to prevent leaking.

The valve style shown in D is representative of the valves used on the car's firewall.  A hole the diameter of the valve body is drilled in the firewall and the valve body is inserted from the boiler side of the firewall and secured by screws in the valve body ears (yes, Stanley firewall construction was wood with a tin covering on the boiler side of the firewall).  The valve stem, packing, packing gland, and packing nut were all installed on the valve body from the dash side of the firewall.  The valve shown still has remnants of nickel plating which these valves often had to dress them up were seen by passengers.

Valve E shows the lace pattern valve wheel which was punched and formed from sheetmetal before being nickel plated.  These valves were used on the early Stanley cars.  Much more common were the valve wheels of cast aluminum construction.  An alternate valve handle design was a wire spring wrapped around a metal hub on the very first cars or the stamped valve wheel found on the last few years of condenser car production.  Stanley valve stem ends were machined with a 1/4" square so that the valve wheel could be peened onto valve stem.

Stanley valve ports were generally tapped to accept 1/8"-27 NTP pipe as most of the examples above depict.  By mounting the valve to a pipe it allowed the pipe to provide support to the valve.  The remaining ports could be made with pipe connections or have a flare compression fitting used.  Some valves were cast with integral flare fittings cast into the valve body as shown in B.  The 45º flare at the end of the fitting required that the tubing be flared to the same 45º angle.  When the fitting nut is tightened it compresses the tubing between the flare on the nut and the flare on the fitting thus providing a clamping action between the tubing and the fitting.  This form of fitting provides increased strength to the connection and insures a large contact surface between the tubing and the fitting allowing the fitting to withstand high pressures and vibration.

See the discussion on the Pilot Valve for additional information on Stanley valves including a discussion on packing valves and pumps.  See the discussion of the Boiler Check Valve for a description of the design and operation of Stanley check valves.  See the article on the Fuel Pressure Relief Valve for a additional discussion on Stanley valves.  See the article on the Burner Fuel System Strainer, Check Valve, and Shut-off for a discussion of the pipe and copper tubing used on Stanley cars.