3500 ENGINE CONTROL ,ELECTRONIC UNIT INJECTION PART.1

3500 ENGINE CONTROLS

ELECTRONIC UNIT INJECTION

INTRODUCTION

This presentation discusses the 3500B Electronic Unit Injection (EUI)
Engine Controls used in machine applications.
The topics are sequenced as follows:
- Introduction and Major Components
- Electronic Control System
- Fuel Supply System
- System Power Supplies
- Electronic Sensors and Systems
- Application Specific Systems.

Overview

The 3500B engines were direct replacements for the original 3500 Series engines. Many additional features and benefits have been incorporated into the 3500B Series which will be described later in the presentation.
The 3500B engines equipped with Electronic Unit Injection (EUI) are available in construction equipment and industrial applications.
Caterpillar machines currently powered by 3500 EUI engines include:

Off-highway Trucks                                      777 - 793
Wheel Loaders                                             992 - 994
Track-type Tractors                                      D11
Excavators                                                    5130 - 5230

This list is generic and includes both the original 3500 Series engines and the 3500B engines.
The 3500 EUI engines have many features and benefits not possible with mechanical fuel systems. These features include a very clean exhaust, improved fuel consumption and cold starting, simplified maintenance with fewer moving parts, and reduced operating costs.

Engine cross sectional view.

This cross sectional view of the engine shows the injector installation and the pushrod arrangement in relation to the upper portion of the engine.
This sectional view is similar to the original 3500 EUI engine. Major differences are the spring loaded injector push rods and the larger diameter camshaft (described later).

EUI Fuel System Components

This schematic shows the various components in the 3500B EUI fuel delivery system. A detailed explanation of the system and the various components follows later in this presentation. The schematic above shows the 3516B fuel system as installed in the 793C Off-highway Truck.
The electronic components in the 3500B EUI fuel system are very similar to those used in other EUI and, to some extent, the HEUI electronic system. However, in this system, the injectors are actuated by camshafts.
The injectors are electronically signalled, as in the original 3500 EUI system.

Electrical block diagram.

This electrical schematic shows the various components in the system and the section of the system in which they are located.
On the left side of the schematic are the engine mounted components, and on the right side of the schematic are the machine mounted components.
The connection between the two circuits is made by the Machine Interface Connector.
Some components or circuits are not used by the fuel system, but are controlled by the engine ECM. For example:
- Pre-lubrication Circuit
- Exhaust Wastegate Control
- Demand Fan Control
- Ether Injection System.

Six major component types

This slide shows six major types of electrical/electronic components in the EUI fuel system:
- ECM
- Throttle Control
- Pressure Sensor
- Temperature Sensor
- Speed/Timing Sensor
- Injector.

The CAT Data Link (not shown) provides a two-way communication path between the EUI system and the other ECM’s or systems on the machine.
The CAT Data Link also allows the ET service tool to communicate with the engine ECM.

NOTE: Only one example of each sensor (pressure and temperature) is shown on the slide.

External Engine Views and Major Components

The engine block is similar to the original 3500 block. The main difference is due to the larger camshaft which needs a larger bore in the block to accommodate the camshaft.
The principal component in the EUI system is the Electronic Control Module (ECM). The ECM (arrow) is mounted at the front of the engine.
The following components are also located on the front of the engine:

- Timing Calibration Connector
- Coolant Flow Sensor
- Turbocharger Outlet Pressure Sensor.

Engine rear view

At the rear of the engine is the timing gear housing containing the following components:
- Aftercooler Temperature Sensor (1)
- Machine Interface Connector (2)
- Speed/Timing Sensor (3)

Engine left side view

On the left side of the engine are the following components:

- Coolant Temperature Sensor (1) on the thermostat housing
- Speed/Timing Sensor (2)
- Fuel filters (3)
- Oil Filters (4)

Additional components mounted on this side of the engine (to be explained later in the presentation) are:

- Exhaust Temperature Sensor (one of two)
- Filtered Oil Pressure Sender
- Unfiltered Oil Pressure Sender2

Engine right side view

On the right side of the engine are the following components:

- Crankcase Pressure Sensor (1)
- Oil Renewal Injector (2)
- Fuel Transfer Pump (3)
- Coolant Flow Switch (4)
- Timing Calibration Connector (5)

Additional components on this side of the engine include:

- Right Exhaust Temperature Sensor
- Oil Level Switch
- Wiring Harness

The wiring harness includes the Deutsch electrical connectors on the cylinder heads. The Deutsch connectors conduct current to the electronic unit injectors through internal wiring in the cylinder heads.

ECM--the "heart" of the system.

The major component in the EUI system is the Electronic Control Module.
The ECM is the "heart" of the engine. The ECM performs engine governing, timing and fuel limiting. It also reads sensors and communicates to the instrument display system through the CAT Data Link.

The Personality Module is located on the rear of the ECM through an access panel.
The Personality Module is used to program the ECM with all the rating information for a particular application. The Personality Module can be changed by direct replacement or can be flash programmed (or reprogrammed) using a PC..

EUI wiring harness

The wiring harness provides two-way communication between the ECM and the engine sensors and connects the ECM to the unit injectors.
The harness is routed from the ECM at the left front of the engine to the left side of the engine. The harness then crosses over to the right rear of the engine and is routed to the right side of the engine.

Coolant temperature (sensor (arrow)

The engine Coolant Temperature Sensor (arrow) is located at the front of the engine on the thermostat housing. This sensor is used with the ECM to control various functions. The following systems or circuits use the Temperature Sensor output to the ECM:

* The Vital Information Management System (VIMS) or Caterpillar Monitoring System Coolant           Temperature Gauge over the CAT Data Link.
* The High Coolant Temperature Warning Alert Indicator and Gauge on the VIMS or Caterpillar           Monitoring System panel. (The information is transmitted over the CAT Data Link.)
* The Engine Demand Fan Control, if installed, uses the sensor signal reference to provide the               appropriate fan speed. The Cat Electronic Technician (ET) status screen for coolant temperature         indication. The Cold Mode engine control (i.e. elevated low idle and timing reference for cold             mode operation).
* The Ether Aid control as a reference for Ether Aid operation.

Electronic Timing Components

This view shows the Speed/Timing Sensor (arrow). The sensor is mounted on the rear gear housing. This sensor is used to calculate engine speed and crankshaft position for
timing purposes.

The sensor is self-adjusting, but special precautions are necessary during installation to prevent damage. (The precautions are described later in the presentation.)

NOTE: After installation, the sensor is initially in contact with the timing wheel.

Identify components

This view shows the Timing Wheel (1) and the Speed/Timing Sensor (2) on the engine. A dowel pin (3) on the camshaft and a corresponding hole on the timing
wheel are used to time the wheel relative to the camshaft. The camshaft is then timed with the crankshaft at TDC.

Notice the wide 50/50 size slot and equal size tooth (4) cut in the wheel.
Three pairs of equal size slots and teeth are on the wheel. The other 21 slots and teeth are 80/20 relative size. These features are used to generate a digital signal necessary for timing. These functions are more fully explained later in the second section of
this presentation. This timing wheel is common to all 3500 engines.

Timing wheel (arrow)

The timing wheel (arrow) is mounted on and driven by the left camshaft
(not shown). The camshaft is driven by the rear gear train, as shown in
this slide.

3500B camshaft

Each cylinder has three corresponding camshaft lobes. The center lobe is is used to actuate the unit injector. The 3500B has a larger diameter camshaft to accommodate the higher injection pressures generated in the unit injector pumps.
The cylinder block has a larger camshaft bore to accommodate the larger camshaft. (All 3500 engines are now being manufactured to this standard.).

injector pushrod spring.

The injectors are actuated by the camshaft. This view also shows the valve train which is on both sides of the injector mechanism below the valve cover.
Notice the 3500B injector pushrod spring, which maintains contact between the lifter roller and the camshaft lobe. This spring is designed to maintain cam follower and camshaft contact and protect the mechanism during a possible overspeed.

3500B EUI injector

The 3500B EUI injector is actuated by the pushrod and rocker arm. Fuel flow is controlled by the ECM through a solenoid on the side of the injector.
The injection cycle is initiated and terminated by the ECM with a 105 Volt signal. The start of injection and, therefore, timing are determined by the start of the signal. The duration of the signal from the ECM (and rpm) determines the quantity of fuel delivered per stroke. This operation is explained in more detail in the Electronic Controls section of the presentation.

Fuel pressure regulator

The Fuel Pressure Regulator (1) is located on the top right side of the engine.
Fuel flows from the fuel filter base, through the steel fuel lines (2), to the EUI fuel injectors. Return fuel from the injectors flows through the fuel pressure regulator before returning to the fuel tank. Fuel pressure is controlled by the fuel pressure regulator.

Atmospheric pressure sensor (arrow)
The Atmospheric Pressure Sensor (arrow) is installed on the ECM mounting adapter and is vented to the atmosphere. This sensor has various functions which are fully described later in the presentation. Briefly, it performs the following functions:

Ambient pressure measurement for automatic altitude compensation and automatic air filter compensation.

Absolute pressure measurement for the fuel ratio control, ET, filter restriction, and Caterpillar Monitoring System panel (gauge) pressure calculations.

Turbocharger inlet pressure sensor.

The Turbocharger Inlet Pressure Sensor (1) is mounted between the air filter and the turbocharger.
This sensor is used in conjunction with the atmospheric pressure sensor to measure air filter restriction for engine protection purposes. The difference between the two pressure measurements is used as the filter differential pressure. The engine ECM uses this calculation to determine whether derating is necessary to protect the engine against the effects of excessive filter restriction.

This function is referred to as Automatic Air Filter Compensation.
Depending on the application and air intake system configuration, either one or two Turbocharger Inlet Pressure Sensors may be used. If the machine is equipped with an ether start system, the ECM will automatically inject ether from the ether cylinders (2) during cranking. The operator can also inject ether manually with the ether switch in the
cab. Ether will only be injected if the engine coolant temperature is below 10°C (50°F) and engine speed is below 1200 rpm.

Turbocharger outlet pressure sensor (arrow)

Also at the front of the engine in the vee is the Turbocharger Outlet (Boost) Pressure Sensor (arrow). This sensor is used with the ECM to control the air/fuel ratio electronically. This feature allows more accurate smoke control which was not possible with previous mechanically governed engines. The sensor reads boost pressure through a tube connecting the sensor to the manifold.
The sensor also allows boost pressure to be read using the electronic service tools.

Exhaust temperature sensor (arrow)

One Exhaust Temperature Sensor (arrow) is mounted below each turbocharger. These sensors are used to warn of possible damaging conditions in the engine caused by excessive exhaust temperature. On the 793C, the sensors enable the ECM to derate the engine.

Filtered lubrication oil pressure sensor (arrow)

Mounted on the rear of the Oil Filter Group is the Filtered Lubrication Oil Pressure Sensor (arrow). This sensor is used to signal oil pressure to the ECM. The sensor is also used by the ECM to generate a low oil pressure warning for the operator.
Mounted at the front of the Oil Filter Group (not shown) is the Unfiltered Lubrication Oil Pressure Sensor. This sensor is used by the ECM with the Filtered Lubrication Oil Pressure Sensor to calculate oil filter differential pressure.
The oil filter differential pressure calculation provides a warning that the oil filters need to be changed. (This system is not designed to be a substitute for regular filter change maintenance requirements.).

Crankcase pressure sensor (arrow)

A Crankcase Pressure Sensor (arrow) may be mounted on the right side
of the engine.
This sensor is used to protect the engine by giving advance warning of a failure (i.e. a piston allowing excessive blowby which could soon cause considerable damage).

Timing calibration sensor (arrow)

The Timing Calibration Sensor (arrow) is installed when required for speed/timing sensor calibration in the flywheel housing.
This sensor (magnetic pickup) is installed in the hole normally reserved for the timing pin. (The pin is used to position the crankshaft with the No. 1 piston at top dead center.)

Machine Mounted Engine Components

Machine mounted components on off-highway trucks include:

- Brake pedal (1)
- Throttle pedal (2)
- Throttle Position Sensor (3)

The Throttle Position Sensor is attached to the throttle pedal. The Throttle Position Sensor provides the throttle position input to the ECM.
The ECM provides an elevated engine idle speed of 1300 rpm when the coolant temperature is below 60°C (140°F). Above 60°C (140°F), the elevated idle rpm is gradually reduced until the coolant temperature reaches 71°C (160°F). Above 71°C (160°F), the engine will idle at 700 rpm.
Increasing the low idle speed helps prevent incomplete combustion and overcooling. To temporarily reduce the elevated idle speed, the operator can depress the throttle momentarily, and the idle speed will decrease to 700 rpm for 10 minutes.
The Off-highway Truck Throttle Back-up Switch allows a "limp home" mode in the event of a throttle circuit failure.

Fuel filters

Two fuel filters are installed on the left side of the engine. The priming pump is installed on the filter housing.
A fuel filter differential pressure switch is installed on the front of the filter housing to provide a warning when the filters need replacement.
It is important that the correct two micron fuel filters are used with this engine.

Other Systems Controlled by the ECM
Although not actually part of the fuel system, the following circuits are also controlled by the ECM.

- Oil Renewal
- Exhaust Wastegate Control
- Engine Oil Prelube
- Variable Speed Fan Control
- Ether Injection System

These circuits are described later in the presentation.

Engine component identification

This schematic identifies the external EUI engine components for the 793C Truck. The components shown on the left side of the schematic are mounted on the engine and those on the right are machine mounted.

Other machines may differ with the mix of sensors and other components. The appropriate Troubleshooting Guide must be used to verify the specific machine components.

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