B350 1 Ton Van V8-5.9L VIN Z (1992)
Main Relay (Computer/Fuel System): Description and Operation
LOCATION
The ASD relay is located in the engine compartment.
PURPOSE
The ASD supplies battery voltage to the fuel pump. It also supplies voltage to the fuel injectors, ignition coil, and O2 sensor heating element.
OPERATION
The ground circuit for the ASD relay is controlled by the engine controller. The engine controller operates the relay by switching the ground
circuit on and off.
The engine controller monitors distributor signal to determine engine speed and compute injector synchronization. If controller does not receive a
distributor signal when ignition switch is in RUN position, it will de-energize (remove ground) from ASD relay. Battery voltage will be cut to the
fuel pump. It will also be cut to the fuel injectors, ignition coil, and O2 sensor heater element.
