Fuel Pressure Regulator
Fuel pressure regulator is connected in series with fuel injectors and is positioned downstream from them. Excess fuel supplied by pump, but not consumed by engine, passes through regulator and returns to fuel tank through fuel return line.
ECA determines required fuel flow rate necessary to maintain prescribed air/fuel ratio for given engine operation by measuring quantity of air entering engine. Computer determines needed injector pulse width (period of time that injectors are energized) and energizes injector to meter quantity of fuel.
VAF system measures intake air quantity with vane airflow meter and integral air charge temperature sensor. Speed/density control system uses Throttle Position Sensor (TPS), Manifold Absolute Pressure (MAP) sensor and Air Charge Temperature (ACT) sensor to determine intake air quantity.
Fuel pressure regulator is attached to fuel supply manifold assembly downstream of fuel injectors. It regulates fuel pressure supplied to injectors. Regulator is diaphragm operated relief valve in which one side of diaphragm senses fuel pressure and other side is subjected to intake manifold pressure.
Fuel pressure is controlled by spring preload applied to diaphragm. Balancing one side of diaphragm with manifold pressure maintains constant fuel pressure at injectors. Excess fuel is by-passed through regulator and returned to fuel tank.
The regulator controls fuel line vapor formation, allows for rapid restarts, assists in engine idle stabilization and maintains fuel pressure when the engine is turned off. On 1.9L engines, fuel pressure is maintained at 14.5 psi (1.0 kg/cm2 ). On 2.5L engines, fuel delivery pressure is maintained at approximately 39 psi (2.7 kg/cm2 ). On all models, this value may vary from unit to unit. Pressure is adjusted at the factory to compensate for differences in fuel flow among injectors.