Intake air heater ISF3.8

The intake manifold of the ISF3.8 engine is provided with a mounting position for an intake air heater of the cold start assist system.

The heater is a cylindrical heating element built into the intake manifold.

The intake air heater is intended to facilitate engine starting at low ambient temperatures.

The preheat system includes the heater actuator (which controls the operation of the power relay) and the "Start Delay" indicator.

The operation of this system before a cold start is referred to as "preheating".

The time interval during which the intake system heater must be switched on depends on the air temperature in the intake manifold when the ignition is switched on, as shown in the figure.

Engine preheat duration

After a cold start, the intake air heater may be switched on for the warm-up period, which is referred to as "post-heating".

The post-heating duration is determined by the average value of the intake manifold temperature sensor readings when the engine is started.

Post-heating is switched off when the vehicle speed reaches 30.5 km/h.

Removal of the intake air heater

1. Disconnect the lead from the battery negative terminal.
2. Remove the air duct.
3. Remove the air intake pipe adapter.
4. Disconnect the connector of the intake air heater of the cold start assist system.
5. Remove the intake air heater of the cold start assist system.
6. Remove the supply circuit terminal.
7. Extract the nylon insulating bush from its recess in the intake manifold.
8. Disconnect the cold start assist system wiring.
9. Unscrew the earth bolt from the cylinder head.
10. Remove the cylindrical intake air heater of the cold start assist system from the intake manifold.

    

11. Clean the cylindrical intake air heater of the cold start assist system.

    

12. Clean the surfaces of the intake manifold and the pipe with a clean cloth, steam and compressed air.

    

13. Check the contact surfaces of the cover of the cylindrical intake air heater of the cold start assist system and of the intake pipe for cracks or other damage.

Installation of the intake air heater

1. Install the intake air heater of the cold start assist system into the intake manifold.
2. Turn the intake air heater of the cold start assist system so that its supply circuit terminal aligns with the hole in the upper part of the intake manifold.
3. Insert the bolt through the hole in the manifold and screw it by hand into the heater.
4. Fit the nylon insulating bush onto the supply circuit terminal of the intake manifold.
5. Screw the terminal into the heater and tighten it. Tightening torque: 8 N·m.
6. Connect the wiring to the intake air heater of the cold start assist system.
7. Install the earth lead and its mounting screw to the intake manifold. Tightening torque: 8 N·m.

   

8. Install the air intake pipe adapter.

   

9. Install the air duct.
10. Connect the lead to the battery negative terminal.

Checking the intake air heater

1. Connect the INSITE diagnostic tool.
2. In the electronic control unit check menus, select the intake air heater check "Intake Air Heater Override".
3. Follow the on-screen instructions to determine the correct condition of the intake air heater and its circuits.
4. To check the operation of the intake air heater, use a non-contact infrared thermometer.

The above materials cover the design, removal, installation and checking of the intake air heater of the cold start assist system of the Cummins ISF3.8 engine: purpose and composition of the preheat system, preheat and post-heat duration, removal and installation procedure for the heater, checking the heater using the INSITE diagnostic tool and an infrared thermometer, as well as the cold start assist system diagrams for GAZ Valdai and PAZ vehicles. The material is intended for diagnostics, fault-finding and repair of the cold start assist system.