Positive Crankcase Ventilation (Pcv) Systems; Pressure-Vacuum Fuel Filler Tube Cap - Chrysler Concorde 1993 Service Manual

25 - 6 EMISSION CONTROL SYSTEMS
top of the bracket. The vacuum and vapor tube con-
nect to the top of the canister (Fig. 6).
Fig. 5 EVAP Canister Bracket
Fig. 6 EVAP Canister Location
DUTY CYCLE EVAP PURGE SOLENOID
The duty cycle EVAP purge solenoid regulates the
rate of vapor flow from the EVAP canister to the
throttle body. The powertrain control module (PCM)
operates the solenoid.
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the so-
lenoid. When de-energized, no vapors are 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 time delay
ends. During closed loop operation, the PCM ener-
gizes and de-energizes the solenoid approximately 5
to 10 times per second, depending upon operating
conditions. The PCM varies the vapor flow rate by
changing solenoid pulse width. Pulse width is the
amount of time the solenoid energizes. The PCM ad-
just solenoid pulse width based on fuel requirements.
The EVAP purge solenoid and bracket attach to
the right inner fender well next to the dash panel (Fig.
7). The top of the solenoid has the word TOP on it. The
solenoid will not operate unless it is installed correctly.
If the vehicle has a 3.5L engine, the EVAP purge
solenoid shares a bracket with the MTV solenoid.
Fig. 7 EVAP Purge Solenoid

PRESSURE-VACUUM FUEL FILLER TUBE CAP

CAUTION: Remove the fuel filler cap to relieve fuel
tank pressure before servicing fuel system compo-
nents.
A pressure-vacuum relief cap seals the fuel tank (Fig.
8). Tightening the cap on the fuel filler tube forms a
seal between them. The relief valves in the cap are a
safety feature. They prevent possible excessive pres-
sure or vacuum in the tank. Excessive fuel tank pres-
sure could be caused by a malfunction in the system or
damage to the vent lines.
The seal between the cap and filler tube breaks when
the cap removed. Removing the cap breaks the seal and
relieves fuel tank pressure.
If the filler cap needs replacement, only use an
original equipment or equivalent unit.
POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEMS
Intake manifold vacuum removes crankcase vapors
and piston blow-by from the engine. Emissions pass
through the PCV valve into the intake manifold ple-
num (Fig. 9 or Fig. 10). The vapors become part of the
calibrated air-fuel mixture, are burned and expelled
with the exhaust gases. The air cleaner supplies make
up air when the engine does not have enough vapor or
blow-by gases.
PCV VALVE
The Positive Crankcase Ventilation (PCV) valve con-
tains a spring loaded plunger. The plunger meters