Deceleration Fuel Cut-Off System
This system cuts off part of fuel flow in idle (or slow) circuit of carburetor preventing overheating and afterburning in exhaust system. The first fuel cut solenoid is kept energized by the ECM whenever engine is running, except when throttle is closed with RPM above 2290. This condition will be sensed by ECM when throttle position switch opens as throttle closes.
With first fuel cut solenoid valve de-energized, the carburetor's slow (or idle) circuit fuel is cut off. This occurs when vehicle is decelerated from 2290 RPM. See Fig 1 and DECELERATION FUEL CUT-OFF SYSTEM OPERATION chart.