0983524 JOHNSON COVER, Exhaust housing, rear

Illustration 1 g02471356
Component view of the catalytic converter
(1) Catalyst substrate
(2) Sleeve Remove catalyst substrate (1) from the catalytic converter. Perform a visual inspection of the catalyst substrate. Look for discoloration, buildup of foreign deposits, and a uniform coating on the surface of the substrate. Record the physical appearance, condition, and the color of the substrate.Note: For applications that require an increased aftertreatment capacity, sleeve (2) may be replaced with an additional catalyst element. If an additional element has been installed on your application, perform a full inspection on both catalyst substrates.Compare the information in Table 1 to the data collected during the inspection.
Table 1
Appearance of the Substrate
Visual Observations Physical Conditions Probable Cause Corrective Action
Tan or light brown to dark brown substrate. Small amount of gray and white ash. Normal exhaust system back-pressure
Temperature differential across the converter is between 0 to 40 °C (0 to 72 °F). Normal operation None
Soft black sooty deposits on substrate.
Carbon fouling of the substrate is apparent. High exhaust system back-pressure
Elevated emissions levels Clogged air filter
Weak ignition voltage
Low cylinder compression Check the air filter for plugging.
Check the performance of the carburetor and the ignition system.
Check the condition of the piston rings and valves.
After the problem has been corrected, operate the engine to clear any buildup from the substrate. Check the emission levels of the engine. If the engine does not meet emission requirements, any buildup and plugging must be cleared from the catalyst substrate. Consult the Dealer Solutions Network before you proceed.
Large amounts of powdery gray and white ash is covering the substrate. High exhaust system back-pressure
Elevated emissions levels The ash originates from high sulfated ash, zinc, and phosphorus compounds that are found in the lube oil. Ensure that the engine oil consumption rate is less than 0.67 g/kW-h (0.5 g/bhp-hr)
Use lube oil that has less than 0.6 percent sulfated ash content, less than 900 ppm zinc content and less than 400 ppm phosphorus content.
After the problem has been corrected, operate the engine to clear any buildup from the substrate. Check the emission levels of the engine. If the engine does not meet emission requirements, any buildup and plugging must be cleared from the catalyst substrate. Consult the Dealer Solutions Network before you proceed.
The substrate is dark bronze or black in color.
Fouling of this type is caused by excess oil in the exhaust. High engine crankcase pressure
Elevated emissions levels Worn piston rings
Worn valve guides Perform the necessary repairs on the engine.
After the problem has been corrected, operate the engine to clear any buildup from the substrate. Check the emission levels of the engine. If the engine does not meet emission requirements, any buildup and plugging must be cleared from the catalyst substrate. Consult the Dealer Solutions Network before you proceed.
White powdery appearance. Excessive emissions levels Engine misfire Perform the necessary repairs on the engine.
After the problem has been corrected, operate the engine to clear any buildup from the substrate. Check the emission levels of the engine. If the engine does not meet emission requirements, any buildup and plugging must be cleared from the catalyst substrate. Consult the Dealer Solutions Network before you proceed. Perform the repairs that are necessary.For additional information related to the catalytic converter, refer to the following information:Reference: Systems Operation, "Catalytic Convertor"Reference: Testing and Adjusting, "Catalytic Convertor Performance - Test"Reference: Testing and Adjusting, "Catalytic Convertor Pressure - Test"