CIS Vacuum Lines

The primary vacuum lines for the CIS system are shown below. Included but not colored, are the vacuum lines for distributor retard or advance, or for lines for other equipment.

Vacuum lines

Orange: Not a vacuum line per se. For the WUR shown, this line is an atmospheric vent, attached above the throttle plate.

Blue: Manifold vacuum connection for the WUR though the thermotime switch. The thermotime switch holds of vacuum to the WUR on cold startup for about 20 - 30 seconds for additional fuel enrichment.

Dark green: manifold vacuum exsists here after engine starts (auxiliary air valve), and after engine warm up (auxiliary air regulator). Until these events, air is being bypassed around the throttle plate through the light green lines. This is the operational bybypass mode for these two components.

Dark green at the lower line of the vacuum control (also called the deceleration valve): vacuum exsists here until the vacuum level at the blue top line exceeds about 18" Hg. Then bypass air flows in the light green line around the throttle plate, adding extra air in the intake manifold preventing an overrich mixture. This addresses an emissions concern.

Vacuum and fuel lines 1980 - 1983

vacuum lines 1980