The mechanism for shutting down the idle system consists of an idle fuel jet, blocked by a needle of an electromagnetic shut-off valve. Fuel supply is stopped when the supply circuit of this shut-off valve is open.
The economizer can only work when the limit switch is connected to «weight», i.e. when the throttle pedal is released, when the dampers are fully closed. In this case, the throttle control lever rests against the mixture quality adjustment screw and closes the limit switch to «mass». It should be noted that in the process of starting a cold engine, the limit switch will not be connected to «weight», as the throttle will be slightly opened by the choke control lever.
At forced idle, if the engine speed begins to increase, then the voltage to the winding of the electromagnetic shut-off valve 1 (see fig. 48) supplied by the electronic control unit until the speed exceeds 2100 or 1700 rpm (depending on the installation option of the control unit), although the limit switch is closed to «mass». At higher engine speeds, the ECM turns off power to the solenoid shut-off valve, which cuts off fuel supply to the idle system.
When the engine crankshaft speed decreases at forced idle to 1900 and 1400 rpm, power is again supplied by the electronic control unit to the valve winding, it opens the fuel supply through the idle jet and the engine gradually enters the idle mode, although the limit switch and closed to «mass».
The electronic control unit is connected by wires to the ignition coil, from where it receives information about the engine speed.
At forced idle, at a crankshaft speed above 1400 or 1900 rpm, at the moment the throttle valve starts to open, the limit switch will move away from «masses», voltage will be applied to the solenoid shut-off valve and fuel supply to the idle system will resume.