What is the function of electric solenoid in the carburetor of caprice classic 1988 year model?

Answer 1

The electric solenoid in the Quadrajet carburetor is called the Mixture Control solenoid and, in short, it meters (controls) the air/fuel ratio. This device helps to reduce emissions and improve fuel economy.

In more detail, the Mixture Control (M/C) solenoid meters the amount of fuel that flows through the idle main metering circuits in the carburetor. The ECM (Electric Control Module) is the car's computer, and it tells the M/C solenoid how much fuel to meter.

The ECM energizes and de-energizes the solenoid ten times per second and may keep it energized longer than it is de-energized. When the solenoid is energized longer than it is de-energized it provides a leaner mixture, and in effect it improves fuel economy. When more fuel is needed it is de-energized longer or completely de-energized.

So, imagine that you are at a stop light and your car is idling. The ECM should energize the solenoid longer than it is de-energized, and less fuel is provided which leans the air/fuel mixture. This can help lower emissions a bit and improve fuel economy.

When the light is green and you press the gas pedal with a moderate amount of force or to the max, the M/C solenoid will be de-energized longer than it is energized (or completely de-energized) which enriches the air/fuel mixture and provides more fuel.

A faulty M/C solenoid will likely be in the de-energized position and it may reduce fuel economy and increase emissions; if the solenoid is somehow stuck in the energized position, engine performance may decrease. In this position it may also be difficult to start the car and it may stall at idle.