Before checking, make sure that the wires are connected correctly to the control unit. For checking, you will need a tachometer that monitors the crankshaft speed and a voltmeter with a measurement range of 0.15 V. The check is performed in the following order.
Disconnect the green wire from the carburetor limit switch and connect the tip of this wire to the "ground". Connect a voltmeter 2 to the control unit (figure 134) using a special adapter connector.
Start the engine and, gradually increasing the crankshaft speed, monitor the voltmeter readings. After starting the engine, the voltmeter should show a voltage of at least 10 V, and at the moment the valve is turned off, a sudden drop in voltage to a value of no more than 0.5 V. After turning off the valve, gradually reduce the speed until the valve is turned on. The voltmeter should show a sudden increase in voltage of at least 10 V. Check using the tachometer whether the valve response frequencies correspond to the frequencies indicated on the control unit.
Set the crankshaft speed within 2200...2300 rpm, disconnect the tip of the wire going to the carburetor limit switch from the ground, and then reconnect it to the ground. When disconnecting the wire from the ground, the valve should turn on, and when connected to the ground, it should turn off.
It is permissible to check the control unit without a voltmeter by the characteristic knock of the valve when switching off and on, respectively, during a smooth increase and decrease in the engine crankshaft speed.