Warm Up Regulator: Description and Operation

Fig. 1 Control Pressure Regulator:

The warm up regulator (control pressure regulator), Fig. 1, consists of a spring controlled flat seat diaphragm-type valve and an electrically heated bimetallic spring.
When the engine is at operating temperature, the warm up regulator maintains a constant control pressure above the control plunger. When the engine is cold and needs a richer air/fuel mixture, the control pressure is lowered, allowing the control plunger in the fuel distributor to rise, and more fuel flows to the injectors.
When the engine is cold, a bi-metallic strip reduces the spring load of the diaphragm. This causes the diaphragm to open and more fuel to flow through the bypass line and to the fuel tank. This action reduces the the control pressure. When the engine is running, current flows through the coil which surrounds the bi-metallic strip. As the strip warms, it bends away from spring, decreases the pressure on the diaphragm, and increases control pressure. When a warm engine is started, there is no reduction in the control pressure, as the strip is affected by the engine temperature.