Cold Starting

The cold start valve opens when the starter motor is running. The time the valve remains open and injecting fuel is governed by the thermo time switch, which monitors engine temperature. The maximum injection time occurs at temperatures below -4°F (-20°C). At higher temperatures, the injection time becomes shorter.
When the starter is operating, relay P11 receives voltage and grounds pin 11 in the oxygen sensor control unit. This causes the control unit to set the modulating valve to a fixed pulse of greater than 92%, causing the valve to remain open and the injectors to receive more fuel. The fuel enrichment continues for three seconds after the engine has started.