D

Dashpot:

DASHPOT A damper device in the carburetor that prevents the throttle from closing as soonas the driver's foot is taken off the gas pedal. This prevents the engine from stalling or prevents an overly rich fuel mixture that would increase hydrocarbon exhaust emissions.



DECEL FUEL SHUTOFF (DFS) - A gas saving
device which operates when rpm is above 1800
and the throttle plate is closed, shuts off the idle
fuel passage in the carburetor. On injected
engines, the injector "on time" is controlled by
the ECA regulating the amount of fuel introducedinto the cylinder.

DECELERATION - A decrease in speed.

DELAY VALVE (DV) - Vacuum restriction used to retard or delay the application of a vacuum signal. Also referred to as "Vacuum Delay Valve (VDV)."


DELAY VALVE-TWO WAY (DV-TW) - A delay valve which functions in both directions.

DISTRIBUTOR MODULATOR SYSTEM (DMS) - System which controls the modulation (advance/retard) of the distributor.

Distributor Modulator Valve Assembly:

DISTRIBUTOR MODULATOR VALVE - A switch assembly used in a variety of applications where it controls and monitors a vacuum. Depending upon the application, distributor modulator valves can be used to dump vacuum, operate shift lights, activate components, block airflow, etc.

DISTRIBUTOR RETARD CONTROL VALVE (DRCV) - Used on engines equipped with the CSSA cold start spark advance system. Used in combination with a CSSA PVS.


DISTRIBUTOR VACUUM ADVANCE CONTROL VALVE (DVAC) - A device used in conjunction with the dual diaphragm vacuum advance unit to advance timing under deceleration conditions.


DISTRIBUTOR VACUUM AND VENT CONTROL VALVE - VACVV-D


DISTRIBUTOR VACUUM VENT VALVE- (DVVV) - Required by some engines to prevent fuel migration to distributor advance diaphragm and to act as a spark advance delay valve.


DIVERTER VALVE - See "Air Bypass Valve."


DUAL CATALYTIC CONVERTER - See "Threeway Catalyst" (TWC).


DUTY CYCLE (DC) - The measurement of the off (high voltage) time of the Ignition Module Signal (IMS) pulse expressed in percent.


DWELL - The angle, in degrees, measured on the distributor cam while the breaker points are closed. In an electronic ignition system, dwell is the amount of time that the primary circuit is completed by electronic circuitry.
DYNAMIC RESPONSE TEST - A Key On/Engine Running test in which a rapid acceleration is applied to the engine and the engine is checked for appropriate throttle movement, change in rpm and change in the intake air flow.