Contents: Increased idle speed ↓ Air damper starting clearance ↓ Unloading device ↓ Intake manifold heater ↓ Thermal switch ↓
Adjustment of idle speed and CO content is described in the chapter "Engine adjustment". Remove the air filter, then adjust the carburetor in the following order:
Increased idle speed
1. Connect the tachometer to the engine (see chapter "Engine adjustment").
2. Turn the high idle cam (A, figure W:12) so that the adjusting screw (B, figure W:12) found himself at the highest level of the fist.
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3. Start the engine without touching the accelerator pedal and note the high idle speed value.
4. If the obtained value is outside the limits specified in the section "Technical data", remove the protective cap and adjust the speed using the adjusting screw (B, figure W:12).
Air damper starting clearance
1. Remove the air damper drive cover with the water box without disconnecting the electric heater wire or cooling system hoses.
2. Open the throttle valve and turn the high idle cam (A, figure W:12) so that the adjusting screw (B, figure W:12) stopped at the highest level of the cam.
3. Using a screwdriver, press the air damper starting clearance adjustment screw and push the air damper rod towards the vacuum relief device until it stops (figure W:13).
4. Check the clearance between the edge of the air damper and the wall of the carburetor diffuser using a drill of the appropriate size (see section "Technical data").
5. If necessary, adjust the gap by turning the adjusting screw (figure W:13).
6. Replace the air damper drive cover; the mark on the lid must be aligned with the mark on the body.
Unloading device
Check the operation of the vacuum unloader as follows.
Remove the air filter and run the engine at idle speed. By closing the choke plate manually, check the operation of the unloader: if the choke closes easily to a gap of 4 mm and then resistance is felt, the unloader is working normally. If the choke closes completely without resistance, the diaphragm of the unloader is torn or there is a leak (air leak) in a vacuum system.
Intake manifold heater
The heater built into the intake manifold can be checked as follows:
1. Disconnect the heater connector near the carburetor
2 Measure the voltage on the disconnected heater wires with a voltmeter. With a cold engine and ignition on, the voltage should be approximately 11.5 V. If the voltage does not match the specified value, check the thermal switch (see below).
3. Measure the resistance between the heater wire and the "ground" (figure W:14). The resistance should be 0.25-0.50 Ohm. If the resistance is different, replace the heater.
Thermal switch
The thermal switch unit, built into the engine cooling system, controls the power supply to the air damper actuator heater and the intake manifold heater depending on the coolant temperature. The unit includes two thermal switches: the red thermal switch controls the automatic air damper actuator heater, and the transparent one controls the intake manifold heater.
Check the operation of the thermal switches using a test lamp. Disconnect the electrical wires and connect the lamp between the wire connector and the thermal switch. With a cold engine and the ignition on, the test lamp should light, otherwise replace the thermal switch. If the lamp lights, remove the thermal switch and hang it in a container of water, leaving it connected to the test lamp circuit. Heat the water, monitoring the temperature - the test lamp should go out at a temperature of 30-40°C (red thermal switch) or 50-55°C (transparent thermal switch). If this is not the case, replace the thermal switch.
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