Colt Wagon 2WD L4-1468cc 1.5L SOHC (1990)
Fuel Pressure Regulator: Description and Operation
Fuel Rail, Injectors, Fuel Pressure Regulator And Components
The fuel pressure regulator is mounted on the fuel rail. The primary function of the regulator is to maintain a constant pressure difference between the
fuel pressure at the injector nozzles and the absolute air pressure (manifold vacuum) in the intake manifold. This is because the ECU meters fuel by
modifying only the "ON" time of the injector. The ECU, during its fuel metering calculations, relies on the pressure differential remaining constant. To
accomplish this goal the regulator has a vacuum line to sense intake manifold pressure. With this input the regulator can control the fuel pressure, in
direct response to intake manifold pressure (vacuum) fluctuations.