Mitsubishi Eclipse 1990 Service Manual page 790

ENGINE AND EMISSION CONTROL
EVAPORATIVE EMISSION CONTROL SYSTEM
GENERAL INFORMATION
The evaporative emission control system prevents
the emission of fuel tank vapors into the atmo-
sphere. When fuel evaporates in the fuel tank,
the vapors pass through vent hoses or tubes to
the charcoal filled EVAP canister. The EVAP canis-
ter temporarily holds the vapors. Through the EVAP
OPERATION
The EVAP purge solenoid regulates the rate of
vapor flow from the EVAP canister to the throttle
body. The PCM controls solenoid operation.
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the
When de-energized, no vapors are
solenoid.
purged. The PCM de-energizes the solenoid during
open loop operation.
The engine enters closed loop operation after it
reaches a specified temperature and the
COMPONENT LOCATION
Evaporative emission purge solenoid
I
purge solenoid, the power-train control module
(PCM) allows intake manifold vacuum to draw va-
pors into the combustion chambers during certain
engine operating conditions. The plunger solenoid
regulates vapor flow from the canister to the engine.
grammed time delay ends. During closed loop
operation, the PCM energizes and de-energizes
the solenoid approximately 5 to 10 times per se-
cond, depending on operating conditions. The PCM
varies the vapor flow rate by changing solenoid
pulse width. Pulse width is the amount of time
the solenoid de-energizes.
PURGE CONTROL SYSTEM CHECK
1
1. Disconnect the vacuum hose from the throttle body and
connect it to a hand vacuum pump.
2. Plug the nipple where the vacuum hose was removed.
3. When the engine is at operating temperature [Engine
coolant temperature:
um at idle to check the condition of the engine and the
vacuum.
Vacuum
53 (15.7
Revision
or higher], apply vacu-
Normal condition
Engine status
right after starting
engine
Vacuum leaks
or more
, seconds later
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is