Sorry mate, Auto Cold Start Device, it is a common abbreivation from the trade. This device hold the throttle on fast idle when cold and can on some vehicles advance the pump/ignition timing, on the 80 they tend to wear and cause a loud ticking noise, they often leaks as well, if left they can break off inside the pump causing extensive damage. Take it off and all will be well, this is similar to the 24v starter system used on the 80, it is completely unnecessary unless you live in Siberia. It is often removed and blanked off resulting in a leak free, quieter and more stable idle. The blanking plate kit is about but I am damned if I can find one here in Spain.
The blanking plate on the Denso injector pump is the same as the blanking plate on a Bosch rotary pump used on dozens of cars and trucks,Golf diesel is probably the most common.
Any fuel injection shop would have a pile of them around somewhere