Electronic Controls
Electronic Control Module
The ECM consists of two main components, the control computer (hardware) and the Personality Module (flash file). The control computer consists of a microprocessor and electronic circuitry. The flash file contains the Engine's operational characteristics. The operating maps influence the engine's performance.
Engine Governor
The ECM governs the engine speed by controlling the amount of fuel that is delivered by the injectors. Refer to Illustration 1. The desired engine speed is determined by input from the throttle switch. Actual engine speed is measured by the engine speed/timing sensors. The ECM changes the duration and timing of fuel injection until the actual engine speed matches the desired engine speed.
Fuel Injection
The ECM controls the timing, the duration, and the pressure of the fuel that is injected. Injection timing depends on engine speed, load, and other operational factors. Fuel is injected ONLY while an injector solenoid is energized by a 105 Volt signal from the ECM. By controlling the timing and duration of the 105 Volt signal, the ECM controls the fuel injection timing, the quantity of fuel and the desired engine speed.
The flash file inside the ECM sets certain limits on the amount of fuel that can be injected. The FRC Limit is a limit that is based on the boost pressure. The boost pressure is calculated as the difference in pressure between atmospheric pressure and turbocharger outlet pressure. The FRC Limit is used to control the air/fuel ratio for control of emissions. When the ECM senses a higher boost pressure, the ECM increases the FRC Limit. A higher boost pressure indicates that there is more air in the cylinder. When the ECM increases the FRC Limit, the ECM allows more fuel into the cylinder.
The Rated Fuel Position is a limit that is based on the power rating of the engine. The Rated Fuel Position is similar to the rack stops and the torque spring on a mechanically governed engine. The Rated Fuel Position determines maximum power and torque values for a specific engine family and a specific rating. The Rated Fuel Position is programmed into the flash file of the personality module at the factory.
Cold Mode Operation
Cold Mode operation automatically stops fuel injection to cylinders that are not firing. Cold Mode operation has the following benefits: increased startability, reduced warm up period and reduced white smoke. The cold cylinder cutout strategy is activated whenever the engine coolant temperature falls below 63 °C (145 °F) and the following conditions are met:
- An engine without the ether option has been running for 10 seconds.
- Ether injection has been completed for 3 seconds.
- The engine has been idling for 10 minutes.
The engine will exit the cold cylinder cutout strategy for 10 minutes under the following conditions:
- Engine speed drops 50 rpm below low idle.
- The throttle switch position is changed.
The engine will exit the cold cylinder cutout strategy under the following conditions:
- The coolant temperature rises above 70 °C (158 °F).
- The Cylinder Cutout Test on the Caterpillar Electronic Technician (ET) is activated.
Electronic Governor
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| Illustration 1 | g00863318 |
Electronic governor | |
Engine Wiring Diagram
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| Illustration 2 | g00870158 |
Location Of The Engine Sensors
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| Illustration 3 | g00863386 |
Left side view (1) Coolant temperature sensor (2) Left hand air shutoff switch (3) Left exhaust temperature sensor (4) Primary engine speed/timing sensor (5) Crankcase pressure sensor (6) Secondary engine speed/timing sensor (7) Aftercooler temperature sensor | |
Location Of The Engine Sensors
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| Illustration 4 | g00863404 |
Right side view (8) Right exhaust temperature sensor (9) Right hand air shutoff switch (10) Unfiltered engine oil pressure sensor (11) Filtered engine oil pressure sensor (12) Unfiltered fuel pressure sensor (13) Filtered fuel pressure sensor | |
Location Of The Engine Sensors
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| Illustration 5 | g00863414 |
Front view (14) Turbocharger compressor outlet pressure sensor (15) Atmospheric pressure sensor (16) Electronic control module (ECM) | |
Location Of The Engine Sensors
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| Illustration 6 | g00863420 |
Rear view (17) Left turbocharger compressor inlet pressure sensor (18) Right turbocharger compressor inlet pressure sensor | |