Chrysler Le Baron, Dodge Dynasty, Plymouth Acclaim. Manual

EVAPORATION CONTROL SYSTEM

The evaporation control system prevents the emis-

sion of fuel tank vapors into the atmosphere. When fuel
evaporates in the fuel tank, the vapors pass through
vent hoses or tubes to a charcoal canister. The canister
temporarily holds the vapors. The powertrain control
module (PCM) allows intake manifold vacuum to draw
vapors into the combustion chambers during certain
operating conditions. The PCM uses the canister purge
solenoid to regulate vapor flow.

On 2.2L and 2.5L TBI, 3.3L, and 3.8L engines,

manifold vacuum purges the vapors at idle as well as
off idle. These engines use a bi-level purge system. The
system uses 2 sources of vacuum remove fuel vapors
from the canister.

Turbo III engines use a tri-level canister purge sys-

tem. In this system, fuel vapors are drawn into the
engine through the throttle body and air cleaner. Fuel
vapors are drawn in at closed throttle, part throttle,
and wide open throttle (in boost).

The 2.5L MPI (flexible fuel AA-Body) and 3.0L have

a duty cycle purge system. The powertrain control
module PCM controls vapor flow by operating the duty
cycle EVAP purge solenoid. Refer to Duty Cycle EVAP
Purge Solenoid in this section.

The evaporative system uses specially manu-

factured hoses. If they need replacement, only
use fuel resistant hose.

PRESSURE RELIEF/ROLLOVER VALVE

All vehicles have a combination pressure relief and

rollover valve. The dual function valve relieves fuel
tank pressure. The valve also prevents fuel flow
through the fuel tank vent valve hoses if the vehicle
accidentally rolls over. All vehicles pass a 360° rollover.

The pressure relief valve opens at a certain pressure.

When fuel tank pressure increases above the cali-
brated pressure, the valve opens to release fuel tank
vapors pressure. The evaporative (charcoal) canister
stores the vapors. For pressure relief/rollover valve
service, refer to the Fuel Tank section of Group 14.

EVAPORATIVE CANISTER

All vehicles use a sealed, maintenance free, evapora-

tive (charcoal) canister. The canister mounts to the
inner wheel well area of the engine compartment (Fig.
4 or Fig. 5).

Fuel tank pressure vents into the canister. The

canister temporarily holds the fuel vapors until intake
manifold vacuum draws them into the combustion
chamber. The canister purge solenoid purges vapors
from the canister at predetermined intervals and en-
gine conditions.

CANISTER PURGE SOLENOID—EXCEPT 3.0L AND
2.5L MPI

The powertrain control module (PCM) operates the

canister purge solenoid (Fig. 6). During warm-up and
for a specified period after hot starts, the PCM
grounds the purge solenoid causing it to energize.
When the PCM grounds the solenoid, vacuum does
not reach the charcoal canister valve.

When the engine reaches a specified operating tem-

perature and the time delay interval has occurred,
the PCM de-energizes the solenoid by turning off the
ground. When the PCM de-energizes the solenoid,
vacuum flows to the canister purge valve. Intake
manifold vacuum purges fuel vapors through the
throttle body. The PCM also energizes the purge so-
lenoid during certain idle conditions to update the
fuel delivery calibration.

DUTY CYCLE EVAP PURGE SOLENOID

Vehicles equipped with a 3.0L engine and the Flex-

ible Fuel AA-Body with the 2.5L MPI engine use a
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 operates the solenoid.

Fig. 4 Evaporative Canister—Except 3.0L and 2.5L

MPI

Fig. 5 Evaporative Canister—3.0L and 2.5L MPI

EMISSION CONTROL SYSTEMS

25 - 13

Chrysler Le Baron, Dodge Dynasty, Plymouth Acclaim. Manual - part 208