5035021 JOHNSON PLATE, OIL GALLERY

Illustration 1 g01228874
System component diagram of HEUI fuel system (typical example) (1) Hydraulic pump (2) Oil flow to engine (3) Oil filter (4) Engine oil pump (5) Oil cooler (6) IAP sensor (7) Injectors (8) Rail for fuel supply (9) Fuel pressure regulator (10) IAP control valve (11) Secondary fuel filter (12) Fuel tank (13) Back of camshaft gear (14) Speed/timing sensors (15) ECM (16) Boost pressure sensor (17) Diagnostic lamp (18) Throttle position sensor (19) Batteries (20) Coolant temperature sensor (21) Data link (22) Optional coolant level sensor (23) Inlet air temperature sensor (24) Optional fuel temperature sensor (25) Oil pressure sensor (26) Alarm/warning lamp (27) Trolling mode switch (28) Slow vessel mode switch (29) Synchronization switch (30) Maintenance clear switch (31) Fuel transfer pump (32) Primary fuel filter/water separatorThe operation of the fuel system of the Hydraulic Electronic Unit Injector (HEUI) is completely different from any other type of fuel system that is actuated mechanically. 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) (15) .This fuel system consists of six basic components:
Hydraulic Electronic Unit Injector (HEUI) (7)
Electronic Control Module (ECM) (15)
Hydraulic Pump (1)
Injection Actuation Pressure Control Valve (10)
Fuel Transfer Pump (31)
Injection Actuation Pressure Sensor (6) Note: The components of the HEUI fuel system are not serviceable. These fuel system components must not be disassembled. Disassembly will damage the components.Component Description
Hydraulic Electronic Unit Injector
The HEUI fuel system utilizes a hydraulically actuated electronically controlled unit injector (7) .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 7 MPa (1015 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.Electronic Control Module (ECM)
Electronic Control Module (ECM) (15) 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. Then, the ECM uses this data in order to make adjustments to the fuel delivery, injection pressure and injection timing. The ECM contains programmed performance maps (software) in order to define horsepower, torque curves and rpm. This software is commonly called the personality module.Some engines use Electronic Control Modules (ECM) (15) with a replaceable computer chip. The software has already been installed in the replaceable computer chip. The C7 Marine Engine does not have a replaceable personality module. The C7 Marine Engine's personality module is a permanent part of the ECM. The personality module of the C7 Marine Engine can be reprogrammed by using the feature of flash programming of the Caterpillar Electronic Technician (ET).ECM (15) logs faults of engine performance. Also, the ECM is capable of running several diagnostic tests automatically when the ECM is used with an electronic service tool such as the ET or the Electronic Control Analyzer Programmer (ECAP).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 is an axial piston design. 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.Injection Actuation Pressure Control Valve (IAP Control Valve)
Injection actuation pressure control valve (10) (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 (15) 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 (10) is an actuator. The IAP Control Valve converts an electrical signal from ECM (15) to the mechanical