900 L4-1985cc 2.0L SOHC Turbo VIN S FI (1984)
Deceleration Fuel Cut Relay: Description and Operation
Fig. 23 Fuel Shutoff System
Deceleration fuel cut is used to help prevent fuel from being injected into the engine when the throttle is closed at engine speeds above approximately
1575 RPM. When the fuel cut system is in operation, air flow which normally passes the air flow sensor plate is diverted by a vacuum valve, causing the
air to bypass the mixture control unit, Fig. 23. This causes the air flow sensor plate to remain in the rest position, cutting off fuel to the injectors and
reducing HC emissions.
Fig. 62 Vacuum Valve
The vacuum valve, Fig. 62, causes air to bypass the flow sensor when the deceleration fuel cut relay is activated, and the relay also signals the oxygen
sensor control system to maintain a fixed pulse ratio of approximately 60%. The deceleration fuel cut relay is activated when the throttle switch closes
with engine speed above 1400-1750 RPM, the relay switch is in the rest position, and when the coolant temperature above 113°F (thermostatic switch
closed). The relay remains activated until engine speed drops below 1300-1450 RPM, or until the acceleration enrichment timer is activated by the
opening of the throttle switch.
Fig. 63 Fuel Shutoff System
See Fig. 63 for a fuel shutoff system schematic.
