To aid starting and prevent white smoke emission at start up, the engines are equipped with an electric heater located at the air inlet casting. Under the proper conditions of jacket water temperature, intake manifold temperature, ignition position, and elapsed time, the electronic control module turns the heater system on. The system is capable of delivering heat for thirty seconds prior to start up, during cranking, and up to seven minutes continuous and thirteen minutes of cycling (ten seconds on, ten seconds off) after the engine has started.
If for any reason the inlet air heater system malfunctions, the engine will still start and run. The only concerns may be the amount of “white smoke” present and the possible need to use an alternative starting aid.
The basic components of the inlet air heater system are: inlet air heater relay, heater element, coolant temperature sensor, intake manifold air temperature sensor, electronic control module, and an indicator lamp.
Location Of Components
(1) Inlet air heater relay. (2) Ground strap (from heater group to the engine). (3) Inlet manifold. (4) Inlet air heater.
Location Of Components
(1) Inlet air heater relay. (5) Coolant temperature sensor.
The inlet air heater relay (1) is located on the inlet manifold cover. It turns the 12 V heater ON and OFF in response to signals from the ECM.
The inlet air heater relay (1) is located between the inlet manifold and the air inlet elbow. The heater element has a ground strap (2) that must be connected to the engine.
There are four conditions that would cause the inlet air heater to be activated.
1. Power up. Regardless of temperature, the heater and heater lamp should come on for two seconds when the ECM is first powered up (lamp check).
2. Preheat mode. When the sum of coolant temperature plus inlet air temperature is less than 25°C (77°F), the ECM will turn the heater and lamp ON for 30 seconds as a preheat cycle, then OFF. If the operator attempts to start the engine before preheat has timed out, the ECM goes to the cranking mode for heater control.
3. Cranking mode. When the engine is cranking, the ECM will turn the heater ON if the sum of coolant temperature and inlet manifold temperature is less than 25°C (77°F). The heater will remain ON while cranking. If the engine fails to start, the ECM reverts to preheat mode and will activate the heater for another 30 seconds.
4. Engine running cycle. After the engine has started, the same combination of inlet air temperature and coolant temperature will determine if the heater remains activated. The engine running cycle has two segments. Continuous mode. The heater remains on steadily for a maximum of 7 minutes after starting. If the same conditions exist, the ECM will shift to on-off mode. The heater is cycled continuously, ON for 10 seconds and OFF for 10 seconds, for a maximum time of 13 minutes, after which the heater is shut off.
Operation when one of the temperature sensors have failed.
1. When the coolant temperature sensor has an open or short circuit, the heater will be activated if inlet air temperature is less than 10°C (50°F).
2. When the inlet manifold air temperature sensor has an open or short circuit, the heater will be activated if coolant temperature is less than 40°C (104°F).
Reactivate heater. When the engine has been warm and is cooling down, if an engine start is attempted, the inlet air heater will be reactivated if the sum of coolant temperature and inlet air temperature has dropped below 25°C (77°F).
If the sum of coolant temperature and inlet air temperature never reaches 35°C (95°F) during the timed 20 minute period, the heater will be turned OFF at the end of the 20 minute period.
Inlet Air Heater Schematic (Typical Example)
(1) Inlet air heater. (2) Inlet air heater relay. (3) Battery. (4) Inlet air heater lamp. (5) Fuse panel. (6) Electronic control module.
Inlet Air Heater Controller Functional Flow Chart