Catalyst Replacement - Jeep J-10 Series 1982 Technical & Service Manual

1K-14 EXHAUST SYSTEMS
platinum and palladium catalyzing agents. Thousands
of pellets are contained in a steel canister. A plug is
provided in the converter to permit replacement of the
pellets should they become ineffective.
This type converter promotes the oxidation of in
completely burned fuel (HC) and carbon monoxide (CO).
The chemical process involved changes HC and CO into
harmless carbon dioxide (CO<>) and water (H2O) vapor
before the exhaust gas is emitted into the atmosphere.
The catalysts that cause the chemical changes are plati
num and palladium.
With pellet-type COC converters, all exhaust gases
flow through the catalytic converter.
The temperature inside a converter is somewhat
higher than the temperature of the exhaust gases when
they are exhausted from the engine. Insulation in the
pellet-type converter keeps the outside skin of the con
verter at approximately the same temperature as the
muffler. Because of its larger mass, the converter stays
hot much longer than the muffler.
The steel catalytic converter body is designed to last
the life of the vehicle. Excessive heat can result in bul
ging or other distortion, but excessive heat will not be
the fault of the converter. A carburetor, air pump or
ignition problem that permits unburned fuel to enter the
converter will usually cause overheating. If a converter
is heat-damaged, the carburetor, air pump, or ignition
problem should be corrected at the same time the con
verter is replaced. All other components of the exhaust
system should also be inspected for heat damage.
rear half is a conventional oxidizing catalytic (COC)
converter. The front half is a three-way catalytic (TWC)
converter.
As with the TWC pellet-type converter (above), main
taining high conversion efficiency for this type con
verter requires that the carburetor provide an air/fuel
mixture ratio of approximately 14.7:1 (fig. 1K-13). This
is the primary function of the Feedback System used in
conjunction with the converter.
ioor
Rg. IK-13 Optimum Air/Fuel Ratio for Conversion Efficiency
CATALYST REPLACEMENT
THREE-WAY CATALYTIC (TWC) PELLET-TYPE CONVERTER D^l Bed (COC and TWC) Monolithic-Type Converter
This type converter utilizes rhodium in addition to
platinum and palladium as oxidizing agents. Rhodium is
a catalyst for oxides of nitrogen (NOx) and changes it
and carbon monoxide (CO) into nitrogen (N2) andcarbon
dioxide (CO2).
Operationally, as the air/fuel mixture is leaned out,
the converter efficiency for changing HC and CO is
increased but is decreased for changing NOx. Enrichen-
ing the mixture increases converter efficiency for chang
ing NOx but decreases it for HC and CO. For this reason,
to optimize the simultaneous conversion of all three, the
carburetor must provide an air/fuel mixture ratio of
approximately 14.7:1 (fig. 1K-13). This is the primary
function of the C4 System that is used in conjunction
with the Three-Way Catalytic (TWC) Converter.
DUAL BED (COC AND TWC) MONOLITHIC-TYPE CONVERTER
The dual bed monolithic-type converter used with six-
cylinder engines is two converters in one container. The
This type converter is not serviceable. The entire unit
must be replaced if defective. Remove by disconnecting
the air injection tube and detaching converter from the
front exhaust pipe and the muffler (or rear exhaust pipe,
if equipped). Install replacement converter.
COC and TWC Pellet-Type Converter
The pressed-in plug must be removed to replace the
pellets. A replacement plug (fig. 1K-14) is required to
seal the converter after the pellets have been replaced.
On-vehicle servicing is the only factory approved
method of replacing pellets because catalytic converters
are difficult to remove from most vehicles, especially
after a large number of miles have accumulated, with
out damaging the converter assembly or exhaust
connections.
The catalyst replacement tool includes an emptying
and fill mechanism, a vacuum aspirator and two hand
tools used for removal of the converter drain plug. The
emptying and fill mechanism clamps directly to the