PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
(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.