CIS Control Pressure Question -- Adjustable WUR Question
 

Why does lowering the control pressure in a CIS fuel system enrich the air/fuel mixture? Intuitively, it seems that if you lower the control pressure then you allow more fuel to flow back to the fuel tank thereby diverting fuel away from combustion.

With respect to making the WUR on a CIS system adjustable, does the "aftermarket" plug adjustment set-up described in detail in many posts on this list allow you to adjust cold control pressure or warm control pressure or both? If I understand correctly, adjusting the plug adjusts the position of the bimetallic strip and the bimetallic strip overrides the spring pressure. Once the strip "heats up", it lifts up off of the plate and allows the internal springs to take over the upper diaphragm pressure. So the strip affects cold control pressure only. If this is correct, how do I adjust ward control pressure via the WUR?

Thanks,
Duane Duclaux
Richmond, VA

Lowering the control pressure takes pressure off the metering pin, thereby allowing more fuel to be introduced to the injectors per given amount of air (richen the mixture). Increasing the control pressure puts more pressure on the metering pin, thereby reducing the amount of fuel to the injectors per volume of air.

The pin on the top of the WUR, when adjusted, will affect the cold and warm pressure because it acts on the bimetallic strip. I think if it is depressed, it will lean out the mixture. Most WUR's can be adjusted on 3 axis - cold, warm and enrichment.