Comprehensive installation instructions for Pressure Safety Switch Z-13061.


A pressure switch should always be used in conjunction with the universal in-line electric fuel pump. ICC Motor Carrier Safety Regulations stipulate that the fuel pump must not continue to operate after the engine stops.

The safety interlock circuit stops the electric fuel pump when the engine stops even though the ignition switch is not turned “Off.” The pressure switch is a single-pole, double-throw, diaphragm-actuated switch. Terminals P (Pump) and S (Start) are normally closed; terminals P (Pump) and I (Ignition) are normally open. This allows the fuel pump to operate and fill the carburetor while the engine is cranking. When oil pressure exists (2-4½ psi), the P and S terminals are opened and the P and I are closed. The diaphragm is treated to withstand pressure up to 150 psi.

If the oil pressure drops below 2 psi, the connection between P and I opens and the fuel pump stops. This also protects the engine from severe damage if an oil line is broken or the oil level in the crankcase becomes extremely low.

Full battery voltage must be available to the pump when the ignition switch is in the start or run position. Do not connect to the ignition coil, as a ballast resistor may be built into the wire. The pressure switch should be installed at a convenient location in the engine oil pressure system. In some instances, it may be necessary to install a “T” fitting below the existing oil gauge sender or dashlight unit. Wires should be 18-gauge insulated, or heavier, routed so as to protect them from exhaust wear, and anchored securely at frequent intervals to prevent chafing.