The idle shut-off mechanism consists of an idle fuel jet closed by a solenoid shut-off valve needle. Fuel supply is stopped when the supply circuit to this shut-off valve is opened.
The economizer can only operate when the limit switch is connected to ground, i.e. when the throttle control pedal is released and the throttle valves are fully closed. In this case, the throttle control lever rests against the mixture quality adjusting screw and closes the limit switch to ground. It should be noted that during cold engine starting, the limit switch will not be connected to ground, since the throttle valve will be slightly opened by the air damper control lever.
At forced idle, if the crankshaft speed begins to increase, then the voltage on the winding of the electromagnetic shut-off valve 1 (see figure 48) is supplied by the electronic control unit until the rotation speed exceeds 2100 or 1700 rpm (depending on the installation option of the control unit), although the limit switch is closed to ground. At higher crankshaft speeds, the electronic control unit turns off the power supply to the electromagnetic shut-off valve, which results in the fuel supply to the idle system being stopped.
When the engine crankshaft speed decreases at forced idle speed to 1900 and 1400 rpm, the electronic control unit again begins to supply power to the valve winding, it opens the fuel supply through the idle jet and the engine gradually enters idle mode, although the limit switch is closed to ground.
The electronic control unit is connected by wires to the ignition coil, from where it receives information about the engine crankshaft speed.
At forced idle speed, when the crankshaft speed is above 1400 or 1900 rpm, at the moment the throttle valve begins to open, the limit switch will move away from the ground, voltage will begin to be supplied to the electromagnetic shut-off valve, and the fuel supply to the idle system will resume.