Diesel engines rely on the heat of compression in order to initiate combustion. Cold engine start-ups may require extra engine cranking time in order to create the necessary heat for igniting the diesel fuel. The following devices exist in order to aid in cold starting the Caterpillar® diesel engine:
| • | The air intake heater |
| • | The ether injection system |
| • | An engine coolant heater |
The air intake heater preheats the air being drawn into the intake manifold as the air passes over an electrically heated grid.
The Caterpillar® diesel engine is equipped with an electric air intake heater grid. The electric air intake heater grid is located at the air intake manifold. This locations provides a pre-heat feature in order to improve cold weather starting and reduce white smoke after startup. The heater control module senses the following conditions:
| • | Engine oil pressure |
| • | Engine coolant temperature |
| • | Elapsed time necessary in order to activate the air intake heater relay |
| The air intake heater relay turns the heater off and on. An air intake heater indicator lamp in the instrument panel lights when the heater is on. |
The ether injection system injects a charge of ether into the intake manifold. Ether has a lower flash point than diesel fuel. Ether assists in building heat in the combustion chamber.
An engine coolant heater is also available in order to aid in the cold engine starting process. Refer to Coolant Heater Description for more information.
Glow plugs are electric heaters that preheat the combustion chambers. The pre-heat feature improves cold engine start ups.
Notice: Never manually spray starting aid fluids into the air intake where the fluid may come in contact with the heater element. This could result in an explosion and/or fire. Use starting fluid only if the vehicle is equipped with the Automatic Ether Injection System or immediate engine damage may result.
When the engine control switch turns to the ON position, the control module automatically energizes the intake heater element for 2 seconds. Failure of the indicator lamp to light for 2 seconds indicates a system malfunction. If the temperature is below 0°C (32°F) the indicator lamp will light for approximately 30 seconds.
When the engine control switch turns to the ON position, the air intake heater relay is energized through the control module. The air intake heater lamp is also energized through the air intake heater relay.
When the air intake heater relay energizes, the relay contacts close. Closing the relay contacts allows current to flow to the air intake heater. The control module will de-energize the air intake heater relay after approximately 30 seconds. The indicator lamp will turn off when the relay contacts open. This action indicates that the following conditions:
| • | The pre-heat cycle is complete |
| • | The cold engine is ready for cranking |
Once the engine starts and the oil pressure exceeds 241 kPa (35 PSI), the heater control module will then activate a timer. The activated timer re-energizes the air intake heater until the coolant temperature switch opens at 49°C (120°F) for a maximum of 7 minutes.
An override feature temporarily disables the oil pressure switch (1) for 30 seconds after the engine control switch turns ON. Disabling the oil pressure switch permits the heater to remain energized during engine cranking.
If the coolant temperature is above 49°C (120°F) the control module will energize the intake heater for 2 seconds. During this time, the intake heater indicator lamp will light, only for a bulb inspection.
For diagnosis of the air intake heater system, refer to the Caterpillar® 3116 Unit Repair Manual.
