Idle Solenoid System

Principles of Gasoline And Disesel Fuel Systems
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(5) Idle Solenoid System (figure 38 on the following page). The idle

solenoid system serves the same purpose as the degasser system. The system

uses a solenoid whose operation is similar to the ones used in the two

preceding paragraphs. The solenoid operates a needle valve that opens and

closes the carburetor idle port. The needle valve is in a normally closed

position. The solenoid is activated when the ignition switch is turned on,

opening the needle valve. The purpose of shutting off the idle system with

the engine is to help eliminate engine dieseling. A sensing switch is

located in the intake manifold to shut off the idle system whenever manifold

vacuum is excessively high, to prevent excess amounts of fuel from being

sucked in through the idle port during deceleration.