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http://members.rennlist.com/jimwms/CIS/CIShome.html
Thermal valve:
Holds off vacuum from the warm-up regulator when engine is started cold ('77 - '79 engines). Power is applied to the thermal valve when engine is started, and approximately 30 seconds later, the valve opens. When the valve is open, vacuum to the WUR is then determined by the intake manifold. --The vacuum holdoff results in a mixture richening at warmup. The inner hose connects to the intake vacuum source and the outer hose to the WUR.
Safety switch on air flow sensor:
This switch prevents fuel pump from running when ignition key is on and the engine is not running.
Operation of the '76 and later relay:
The relay has two sets of contacts - Normally Open (NO) and Normally Closed (NC). In electrical lingo, "Normal" infers no power on the relay coil. On the basic Porsche round relay, pin 87 is NO, pin 87a is NC and pin 30 is the "arm" of the contact that switches between the two.
Relay Connections:
The fuel pump is connected to pin 30 of the relay socket. (Note that you can't jumper power to the fuel pump by jumpering +12 Volts to a fuse on the fuse panel. The fuse which protects the fuel pump is in the wiring that goes from the NC contact to the ignition switch). +12 Volts from the starter terminal of the ignition switch goes to the NO contact and +12 volts from the "Run" terminal goes to the "hot" end of the relay coil (pin 86) and to the NC contact. The "cold" end of the relay coil (pin 85) goes to the Safety Switch on the air flow sensor housing, and the other contact of the Safety Switch goes to ground. The switch is closed when the airflow sensor plate is at rest (engine not running).
Operational Sequence:
Ignition switch turned to "Run" (Not Start) - Relay energized. Relay contact pulled to the NO position.
Ignition switch turned to "Start" - Starter voltage goes to fuel pump through the NO contact. Fuel pump runs while engine is cranked.
Engine starts and ignition switch released from "Start" position - The Safety Switch opens as the air flow sensor plate rises off its stop. This de-energizes the relay coil, and the relay arm flips back to NC, sending voltage from the "Run" terminal of the ignition switch though the fuse and through the NC contact to the fuel pump. Engine is running, fuel pump is running.
Engine dies due to accident or other malfunction - Airflow sensor plate goes to its stop, closing the Safety Switch, and energizing the fuel pump relay (remember the ignition is still on). Relay pulls the contact back to the NO position. But since there is no voltage on this contact from the starter, fuel pump is disabled.
Control pressure regulator (also called Warm Up Regulator):
Drops control pressure when engine is cold, resulting in a richer mixture during warm up. . The term warm-up regulator is a bit of a misnomer in that this component actually regulates control pressure the entire time the engine is running. It changes the pressure during the warm-up period. Power is applied to bimetal strip in the regulator when fuel pump is on. As the internal resistor heats up the strip, the control pressure supplied to the fuel distributor increases, leaning the fuel mixture. On cars with vacuum control, the WUR enriches mixture under load determined by lower intake manifold vacuum. Some versions also modify pressure with altitude. Lambda sensor systems don't use the vacuum chamber because of this adjustment being automatically accomplished by the lambda system electronics box. '81 saw a change in the internal resistor configuration for the WUR. A second resistor was added to heat the bimetallic spring, controlled by a bimetallic switch. This allows the mixture to lean out more quickly after start-up,about 2 minutes compared to the former 3 minutes.