DTC P0087: Fuel Rail / System Pressure - Too Low: Description

The D-4S (Direct injection 4-stroke gasoline engine Superior) has two fuel injection systems. One is the port fuel injection system The other is the direct fuel injection system The direct fuel injection system has three functions:

1. In the regulating function, the fuel pump for high pressure builds up and regulates the fuel pressure. The fuel pump for high pressure has a plunger and a spill control valve. The plunger reciprocates by the camshaft rotation and pumps the fuel into the direct fuel injectors. The spill control valve regulates the fuel flow from the fuel tank to the plunger When the spill control valve opens (ON), the fuel pressure rises The engine control module (ECM) controls the injector driver to maintain the fuel pressure at 4000 to 13000 kPa (40.8 to 132.6 kgf/cm² , 580 to 1885 psi).
2. In the limiting function, the fuel relief valve mechanically opens to release the fuel pressure when the fuel pressure exceeds 15.3 MPa (156.0 kgf/cm² , 2219 psi).
3. In the releasing function, the ECM opens the fuel relief valve for a few seconds to release the fuel pressure immediately after the power switch is turned OFF. This prevents fuel leaks from the direct injector while the engine is stopped.
   Fig 1: Direct Fuel Injection System Diagram

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