C-12 Engine Caterpillar

The C-12 truck engine has the following characteristics: direct fuel injection, electronic unit injection that is mechanically actuated, turbocharged and air-to-air aftercooled (ATAAC).

The electronic engine control system provides the following functions: electronic governing, automatic air to fuel ratio control, torque rise shaping, injection timing control and system diagnostics.

Several programmable features are included in the electronic control: cruise control, governing the PTO, vehicle speed limiting, rpm limit for high gears, rpm limit for low gears, top engine limit, idle shutdown timer and control for the engine retarder (compression brake).

Additional benefits provide engine fuel economy, serviceability, and operator comfort. The additional benefits include the following features: improved cold starting capability, resistance to tampering, diagnostics, progressive shift engine speed control, data link (SAE J1587) for the American Trucking Association (ATA) and optional Engine Monitoring Package.

An electronic governor controls the output of the unit injectors in order to maintain the engine rpm that is desired. The functions of the governor include a programmable low idle and a 20 rpm to 200 rpm governor overrun.

Very high injection pressures are produced by electronically controlled, mechanically actuated unit injectors. The injectors combine the pumping and the electronic fuel metering (duration and timing) during injection. The unit injectors accurately control smoke limiting, white smoke, and engine acceleration rates.

There is one unit injector per cylinder. Individual unit injectors meter the fuel. The individual unit injectors also pump the fuel. The metering and the pumping is done under high pressure. High injection pressures help to reduce fuel consumption and emissions. The use of this type of unit injector provides total electronic control of injection timing. The injection timing varies with engine operating conditions. The engine performance is optimized in the following areas:

• starting

• emissions

• noise

• fuel consumption

• driveability

The timing advance is achieved through precise control of the injector firing. Engine speed is controlled by adjusting the firing duration. The information is provided to the Electronic Control Module (ECM) by a speed timing sensor. The information is for detection of cylinder position and engine speed.

The engines have built-in diagnostics in order to ensure that all of the components are functioning and operating properly. In the event of a system component deviation from the programmed limits, the operator will be alerted to the condition by a CHECK ENGINE/DIAGNOSTIC lamp that is mounted on the dashboard. An electronic service tool that is provided by Caterpillar or the cruise control switches (if equipped) may be used to read the numerical code of the diagnostic flash code. There are three types of diagnostic codes: ACTIVE, LOGGED and EVENT. These codes are logged and stored in the ECM. Refer to the Operation and Maintenance Manual, "Engine Diagnostics" for additional information.

The cooling system consists of the following items: a centrifugal pump that is driven by a gear, water temperature regulator, an oil cooler and an OEM supplied radiator that incorporates a shunt system.

The engine lubricating oil is supplied by a gear type pump. The engine lubricating oil is cooled and filtered. Bypass valves provide unrestricted flow of lubrication oil to the engine parts when the oil viscosity is high or if either the oil cooler or the oil filter elements (paper cartridge) become plugged.

Engine efficiency, efficiency of emission controls, and engine performance depend on adherence to proper operation and maintenance recommendations. This includes the use of recommended fuels, coolants, and lubrication oils.

Multitorque Rating (If Equipped)

The multitorque ratings provide additional torque as engine load increases. This feature provides higher torque levels. This feature also provides better driveability while the truck is only in the top gears. The engine electronics are able to determine when the vehicle is in the top gears by calculating the engine rpm/vehicle speed ratio.

With the additional torque, the following benefits are provided: less shifting in rolling terrain, less wear on drive line components, more responsive and better engine performance.

Welding and Cat Electronic Engines

To help avoid damage to the electronic controls, proper welding procedures are necessary. Before welding on a vehicle that is equipped with an electronic engine, observe the following precautions:

1. Turn off the engine. Place the key start switch in the OFF position.

2. If the vehicle has a battery disconnect switch, open the switch. Otherwise, disconnect the negative "-" battery cable from the battery of the vehicle.

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NOTICE
Do not ground the welder to electrical components such as the ECM or sensors. Improper grounding can cause damage to the drive train bearings, hydraulic components, electrical components, and other components. Clamp the ground cable from the welder to the component that will be welded. Place the clamp as close as possible to the weld. This will help reduce the possibility of damage.

1. Clamp the ground cable from the welder to the component that will be welded. Place the clamp as close as possible to the weld.

2. Protect wiring harnesses from welding debris and from spatter. Use proper welding procedures.