PISTON 7Y1867 - Caterpillar

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(1) Oil pump (2) Hydraulic electronic unit injectors (3) Oil filter (4) Oil cooler (5) High-pressure oil (6) Fuel (7) Connector for the Injection Actuation Pressure Control Valve (IAPCV) (8) Unit injector hydraulic pump (9) Sensor for the Injection Actuation Pressure (IAP) (10) Fuel filter (11) Primary fuel filter and water separator (12) Fuel tank (13) Camshaft gear (14) Speed/Timing sensors (15) Electronic Control Module (ECM) (16) Battery (17) Fuel pressure regulator (18) Boost pressure sensor (19) Oil pressure sensor (20) Coolant temperature sensor (21) Throttle position sensor (22) Inlet air temperature sensor (23) Atmospheric pressure sensor (24) Air inlet heaterIntroduction
The operation of the Hydraulic Electronic Unit Injector fuel system is different from any other fuel system that is actuated mechanically. The HEUI fuel system is free of adjustment. Adjustments to the components that are mechanical cannot be made. Changes in performance are made by installing different software in the Electronic Control Module (ECM).This fuel system consists of four basic components:
Hydraulic Electronic Unit Injector (HEUI)
ECM
Unit injector hydraulic pump
Fuel transfer pumpNote: The fuel transfer pump is a serviceable part. The internal components of the HEUI fuel system are not serviceable. These fuel system components must not be disassembled. Disassembly will damage the components. If the components have been disassembled, Caterpillar may not allow a warranty claim or Caterpillar may reduce the warranty claim.Component Description
Hydraulic Electronic Unit Injector
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The fuel system utilizes a hydraulically actuated electronically controlled unit injector.All fuel systems for diesel engines use a plunger and barrel in order to pump fuel under high pressure into the combustion chamber. The HEUI uses engine oil under high pressure in order to power the plunger.The HEUI uses engine lubrication oil that is pressurized from 6 MPa (870 psi) to 28 MPa (4061 psi) in order to pump fuel from the injector. The high-pressure oil is called the injection actuation pressure. The HEUI operates in the same way as a hydraulic cylinder in order to multiply the force of the high-pressure oil. This multiplication of pressure is achieved by applying the force of the high-pressure oil to a piston. The piston is larger than the plunger by approximately six times. The piston that is powered by engine lubrication oil under high pressure pushes the plunger. The actuation pressure of the oil generates the injection pressure that is delivered by the unit injector. Injection pressure is greater than actuation pressure of the oil by approximately six times.Low actuation pressure of the oil results in low injection pressure of the fuel. High actuation pressure of the oil results in high injection pressure of the fuel. ECM
The ECM is located on the left side of the engine. The ECM is a powerful computer that provides total electronic control of engine performance. The ECM uses data from engine performance that is gathered by several sensors. The ECM uses this data in order to adjust the fuel delivery, injection pressure, and injection timing. The ECM contains programmed performance maps (software) in order to define horsepower,