The main node of the system is the electronic control unit 3 (pic. 133). It receives information through two channels. First, from the limit switch 2 of the carburetor about the position of the first throttle. This switch connects to «weight» conclusion «5» control unit with the damper closed. Second, from the ignition coil 1 about the crankshaft speed. This information comes in the form of voltage pulses taken from the primary winding of the ignition coil. The control unit takes into account all this information and at the given moments gives out a voltage that turns on the carburetor solenoid valve.
Pic. 133. Connection diagram of the carburetor solenoid valve control system:
1 - ignition coil; 2 - limit switch in the carburetor; 3 - control unit; 4 - solenoid valve; 5 - mounting block; 6 - ignition switch.
When the carburetor limit switch is not closed to «mass», i.e. the first throttle valve is not closed, then the control unit supplies voltage to the solenoid valve at any crankshaft speed. If the limit switch is closed to «mass» (damper fully closed), then in this case the activation of the solenoid valve depends on the speed of the crankshaft. If at the moment of closing the first throttle valve the speed was higher than 2100 rpm, then the control unit will turn off the solenoid valve, and turn it on only when the speed drops to 1900 rpm.