0320172 JOHNSON SHAFT, Shifter

Illustration 1 g00730195
HEUI Component Diagram (1) Hydraulic pump. (2) Oil flow to engine. (3) Engine oil pump. (4) Injectors. (5) Oil filter. (6) Oil cooler. (7) IAP control valve. (8) IAP sensor. (9) Fuel supply rail. (10) Fuel transfer pump. (11) Secondary fuel filter. (12) Fuel tank. (13) Fuel pressure regulator. (14) Primary fuel filter/water separator. (15) Back of cam gear. (16) Speed/timing sensors. (17) Turbocharger inlet pressure sensor. (18) Throttle position sensor. (19) Batteries. (20) ECM. (21) Coolant temperature sensor. (22) Engine oil temperature sensor. (23) Data link. (24) Inlet air temperature sensor. (25) Fuel pressure sensor. (26) Oil pressure sensor. (27) Turbocharger outlet pressure sensor. (28) Atmospheric pressure sensor.This engine is equipped with hydraulic electronic unit injectors (HEUI). The operation of the HEUI fuel system is completely different from the operation of other fuel systems that are mechanically actuated. The HEUI fuel system is completely free of adjustment. Adjustments to the components that are mechanical can not be made. Changes in performance are made by installing different software in Electronic Control Module (ECM) (20) .This fuel system consists of six basic components:
Hydraulic Pump (1)
Hydraulic Electronic Unit Injector (HEUI) (4)
Injection Actuation Pressure Control Valve (7)
Injection Actuation Pressure Sensor (8)
Fuel Transfer Pump (10)
Electronic Control Module (ECM) (20) Note: The 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 Pump
Hydraulic pump (1) (high pressure oil pump) is located at the left front corner of the engine. The hydraulic pump is a piston pump that has a fixed displacement. The hydraulic pump uses an axial piston. The hydraulic pump uses a portion of the engine lubrication oil. The hydraulic pump pressurizes the engine lubrication oil to the injection actuation pressure that is required in order to power the HEUI injectors.Hydraulic Electronic Unit Injector
The HEUI fuel system utilizes a hydraulically actuated electronically controlled unit injector (4) .All fuel systems for diesel engines use a plunger and barrel in order to pump fuel under high pressure into the combustion chamber. This fuel is pumped into the combustion chamber in precise amounts in order to control engine performance. The HEUI uses engine oil under high pressure in order to power the plunger. All other fuel systems use a fuel injection pump camshaft lobe in order to power the plunger. Because the HEUI is much different, a technician must use different troubleshooting methods.The HEUI uses engine lubrication oil that is pressurized from 6 MPa (870 psi) to 24 MPa (3500 psi) in order to pump fuel from the injector. The HEUI operates in the same way as a hydraulic cylinder in order to multiply the force of the high pressure oil. By multiplying the force of the high pressure oil, the HEUI can produce injection pressures that are very high. 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 on the plunger. This engine lubrication oil under high pressure is called the actuation pressure of the oil. 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. During conditions of low speed such as idle and start, low injection pressure is utilized. High actuation pressure of the oil results in high injection pressure of the fuel. During conditions of high speed such as high idle and acceleration, high injection pressure is utilized.There are many other operating conditions when the injection pressure is between the minimum and the maximum. Regardless of the speed of the engine, the HEUI fuel system provides infinite control of injection pressure.Injection Actuation Pressure Control Valve (IAP Control Valve)
Injection actuation pressure control valve (7) (IAP Control Valve) is located on the side of hydraulic pump (1). Under most conditions, the pump is producing excess oil flow. The IAP Control Valve discharges excess pump flow to the drain in order to control injection actuation pressure to the desired level. The IAP Control Valve is a valve of high precision that controls the actual actuation pressure. The performance maps of ECM (20) contain a desired actuation pressure for every engine operating condition. The ECM sends a control current to the IAP Control Valve. The control current should make the actual actuation pressure equal to the desired actuation pressure.IAP Control Valve (7) is an actuator. The IAP Control Valve converts an electrical signal from ECM (20) to the mechanical control of a spool valve in order to control pump outlet pressure.Injection Actuation Pressure Sensor (IAP)
IAP Sensor (8) is installed in the high pressure oil manifold. The high pressure oil manifold supplies actuation oil in order to power the unit injectors. The IAP Sensor monitors injection actuation pressure. The IAP Sensor sends a continuous voltage signal back to ECM (20). The ECM interprets the signal. The ECM is aware of the injection actuation pressure at all times.Fuel Transfer Pump
Fuel transfer pump (10) is mounted on the back of hydraulic pump (1). The fuel transfer pump is used in order to draw fuel from fuel tank (12). Also, the fuel transfer pump is used in order to pressurize the fuel to 450 kPa (65 psi). The pressurized fuel is supplied to injectors (4) .Fuel transfer pump (10) is a simple gear pump. Fuel transfer pump (10) contains an integral pressure relief valve. Fuel pressure is typically limited between 400 kPa (60 psi) and 830 kPa (120 psi). Excess fuel flows from the pressure relief valve through an internal passage to the inlet side of the pump. The pressure relief valve is on the outlet side of