Contents: Checking the work ↡ Checking the delay time ↡
A cold engine receives a particularly rich hot mixture when starting, making it easier to start. When the engine is running, the Pull-down device closes the enrichment valve under vacuum to prevent the mixture from becoming too rich. The thermal delay valve determines when the Pull-down device is activated after the engine has started. While the Pull-down device is already active when the engine is warm, at low temperatures the valve "delays" the activation moment.
Warm up the engine to operating temperature. The oil temperature should be 70-80°C.
Checking the work
Remove the vacuum hose (50) from the carburetor.
Draw air from the vacuum hose with your mouth, making sure no air passes through. Otherwise, the sealing ring in the thermal delay valve (23) is defective or the bimetallic plate of the valve does not turn on. In this case, replace the valve. Other parts: 27 - air tube for the thermal delay valve.
Remove the thermal delay valve.
Cool the valve, for example, under a stream of water, while sucking air through the vacuum hose located in the middle of the valve. As soon as the valve temperature drops below +20°C, the air flow should turn on. Otherwise, the bimetallic plate of the valve is defective, replace the valve.
Checking the electric heating
Reinstall the thermal delay valve. Attach the test hose to the middle connection pipe of the valve.
Start the engine (assistant) and simultaneously suck air through the test hose. After a few seconds the valve should click and there should be no more air flow.
If the valve does not turn on, remove the plug (84) and, with the engine running, connect the test lamp between its contacts. If the lamp lights up, replace the thermal delay valve, otherwise check the 8 A fuse in the additional fuse box and the wires with connectors according to the wiring diagram. The additional fuse box is located either on or near the relay board at the left pillar. It includes 2 fuses (second fuse 25A). Other details!: (254) - thermal delay valve; (25) - tension screws for the starter cover (18).
Checking the delay time
Test condition: Temperature of thermal delay valve is less than +20°C, engine is cold.
Remove the hose (50) from the carburetor and draw air through it. There should be air flow.
At the same time, start the engine (assistant) and measure the stop time until the valve switches, when there is no more air flow.
The measured time is the delay time. Compare this time with the reference time shown in the diagram. For example: Ambient temperature +15°C, the measured time is about 6 seconds, therefore within the permissible range. The valve is OK in terms of delay time. The permissible range of times at -15°C is between 10 and 16 seconds.
If the valve does not turn on or the turn-on time is outside the permissible range, then with the engine running, remove the thermal delay valve plug and check the voltage and ground connections on the plug with a voltmeter. To do this, connect the voltmeter to the red-black wire and ground, then connect the voltmeter to the brown wire (-) and to the positive pole of the battery. If both times the battery voltage is shown (about 12 V), then replace the thermal delay valve. Otherwise, check the 8 A fuse in the additional fuse box and the electrical connections according to the diagram.