RING-WEAR 9J1159 - Caterpillar

Illustration 1 g00990048
HEUI fuel system (typical example)
(1) Unit injector hydraulic pump
(2) Oil flow to the engine
(3) Oil filter
(4) Engine oil pump
(5) Injectors
(6) Oil cooler
(7) IAP control valve
(8) IAP sensor
(9) Fuel transfer pump
(10) Secondary fuel filter
(11) Fluid manifolds
(12) Fuel tank
(13) Fuel pressure regulator
(14) Speed-timing wheel
(15) Engine speed/timing sensors
(16) Primary fuel filter
(17) Water separator
(18) Oil temperature sensor
(19) Engine boost pressure sensor
(20) Coolant temperature sensor
(21) Coolant level sensor
(22) Oil pressure sensor
(23) Fuel pressure sensor
(24) Fuel temperature sensor
(25) Atmospheric pressure sensor
(26) Throttle position sensor
(27) Data link
(28) Alarm warning lamp
(29) Diagnostic lamp
(30) Electronic Control Module (ECM)
(31) BatteriesThe operation of the Hydraulic Electronic Unit Injector (HEUI) fuel system utilizes the concepts of hydraulics and the multiplication of force to deliver fuel to the engine. The HEUI fuel system is completely free of adjustment. Adjustments cannot be made to the mechanical components of the system. Changes in performance are made by installing different software in Electronic Control Module (ECM) (30).This fuel system consists of six basic components:
Hydraulic Electronic Unit Injector (HEUI) (5)
Electronic Control Module (ECM) (30)
Unit injector hydraulic pump (1)
Injection actuation pressure control valve (7)
Fuel transfer pump (9)
Injection actuation pressure sensor (8)Note: The components of the HEUI fuel system are not serviceable components. 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
The HEUI fuel system utilizes a hydraulically actuated electronically controlled unit injector (5).The precise delivery of the fuel controls the engine's performance. All fuel systems for diesel engines use a plunger and barrel in order to pump high pressure fuel into the combustion chamber. A fuel injection pump camshaft lobe is typically used to provide a mechanical force to the plunger. The plunger then pumps the precise amount of fuel into the combustion chamber. The HEUI fuel system uses engine oil that has been pressurized by the system's hydraulic pump in order to apply force to the plunger. Control for the exact timing of the fuel delivery is provided electronically by the engine's ECM. Due to the differences in the HEUI fuel system, a technician must use different troubleshooting methods in order to diagnose fuel system problems.The HEUI fuel system's hydraulic pump pressurizes the engine lubrication oil from 10 MPa (1450 psi) to 23 MPa (3350 psi) in order to transfer force from the engine's rotational energy to hydraulic energy that is used by the injector. The HEUI fuel system operates in the same manner as a hydraulic cylinder. A piston in the injector is used to receive the hydraulic energy that is supplied by the pump. The piston converts the hydraulic energy to a mechanical force that is applied directly to the injector's plunger assembly. The plunger assembly multiplies the mechanical force that is provided by the piston. The plunger converts the force into a hydraulic pressure that is placed on the fuel that is in the injector barrel. By multiplying the force of the high