Fuel Control
An electric, positive-displacement, roller vane type fuel pump is located in the fuel tank. The fuel pump is an integral part of the fuel gauge sending unit. The fuel pump supplies fuel to the fuel rail. A fuel pressure regulator, mounted downstream of injectors on fuel rail, maintains fuel system pressure at a constant 36 psi (2.5 kg/cm2 ) pressure. See CANISTER PURGE SOLENOID under EMISSION CONTROL in this article for more information.
Power to the fuel pump is supplied by the SMEC via the Automatic Shutdown (ASD) relay. The SMEC is supplied with an operating signal from the distributor. When the SMEC senses a distributor signal during cranking, it grounds the ASD closing contacts. This completes the circuit for the electric fuel pump, injectors and ignition coil. If the distributor signal is lost for any reason, the ASD relay shuts off this circuit in less than one second; preventing fuel, spark and engine operations.
The electrically pulsed fuel injectors supply fuel to each cylinder. The SMEC provides power to each group of injectors (2 injectors per group). The SMEC determines when to energize each group of injectors, and how long each injector remains open (pulse width) based upon engine operating conditions.
When electrical current is supplied to the injector, an integral armature and pintle valve move a short distance against a spring, opening a small orifice. Fuel supplied to the injector is forced around the pintle valve and through this opening, resulting in a fine spray of fuel in the shape of a hollow cone. The injector pulse width (injector "on" time) determines the amount of fuel entering the engine and, therefore, the air fuel ratio.