On Acceleration

When accelerating the intake manifold pressure deviation is sensed by the fuel enrichment pressure switch.
When the engine is cold, the fuel enrichment is provided by the cold start valve. When the engine is cold, the cold start valve is operated until the engine coolant temperature reaches 77 °F (25°C), when the thermo time switch opens the ground circuit to the cold start relay. If the coolant temperature reaches 77 °F (25°C) within two minutes of starting, the P11 relay will operate, opening the modulating valve and providing the injectors with additional fuel.
When the engine is hot, the fuel enrichment is provided when the pressure switch closes, sending a voltage signal to the P11 relay. The P11 relay senses that the thermo time switch is open and grounds pin 11 of the oxygen sensor control unit, thereby keeping the modulating valve open and increasing the amount of fuel pressure available for injection.