Chrysler 2004 Concorde Service Manual page 1629

LH
PCV VALVE (Continued)
OPERATION
When the engine is not operating or during an
engine backfire, the spring forces the plunger back
against the seat. This prevents vapors from flowing
through the valve (Fig. 12).
Fig. 12 Engine Off or Engine Backfire No Vapor
When the engine is at idle or cruising, high mani-
fold vacuum is present. At these times manifold vac-
uum is able to completely compress the spring and
pull the plunger to the top of the valve (Fig. 13). In
this position there is minimal vapor flow through the
valve.
Fig. 13 High Intake Manifold Vacuum Minimal Vapor
During periods of moderate intake manifold vac-
uum the plunger is only pulled part way back from
the inlet. This results in maximum vapor flow
through the valve (Fig. 14).
Fig. 14 Moderate Intake Manifold Vacuum Maximum
Vapor Flow
DIAGNOSIS AND TESTING - PCV SYSTEM
WARNING: APPLY
BLOCK WHEELS BEFORE PERFORMING ANY TEST
OR ADJUSTMENT WITH THE ENGINE OPERATING.
Flow
Flow
PARKING BRAKE
(1) With engine idling, remove the hose from the
PCV valve. If the valve is not plugged, a hissing
noise will be heard as air passes through the valve. A
strong vacuum should also be felt when a finger is
placed over the valve inlet.
(2) Install hose on PCV valve. Remove the
make-up air hose from the air plenum at the rear of
the engine. Hold a piece of stiff paper (parts tag)
loosely over the end of the make-up air hose.
(3) After allowing approximately one minute for
crankcase pressure to reduce, the paper should draw
up against the hose with noticeable force. If the
engine does not draw the paper against the grommet
after installing a new valve, replace the PCV valve
hose.
(4) Turn the engine off. Remove the PCV valve
from intake manifold. The valve should rattle when
shaken.
(5) Replace the PCV valve and retest the system if
it does not operate as described in the preceding
tests. Do not attempt to clean the old PCV valve.
If the valve rattles, apply a light coating of Loctite
Pipe Sealant With Teflon to the threads. Thread the
PCV valve into the manifold plenum and tighten to 7
N·m (60 in. lbs.) torque.
VAPOR CANISTER
OPERATION
All vehicles use a maintenance free, evaporative
(EVAP) canister. Fuel tank vapors vent into the can-
ister. The canister temporarily holds the fuel vapors
until intake manifold vacuum draws them into the
combustion chamber. The Powertrain Control Module
(PCM) purges the canister through the proportional
purge solenoid. The PCM purges the canister at pre-
determined intervals and engine conditions.
Purge Free Cells
Purge-free memory cells are used to identify the
fuel vapor content of the evaporative canister. Since
the evaporative canister is not purged 100% of the
time, the PCM stores information about the evapora-
tive canister's vapor content in a memory cell.
The purge-free cells are constructed similar to cer-
tain purge-normal cells. The purge-free cells can be
monitored by the DRB III Scan Tool. The only dif-
ference between the purge-free cells and normal
adaptive cells is that in purge-free, the purge is com-
pletely turned off. This gives the PCM the ability to
compare purge and purge-free operation.
AND/OR
EVAPORATIVE EMISSIONS 25 - 17