0438272 JOHNSON CARBURETOR ASSY.

Recommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps Values Results
1. Incorrect Maintenance Intervals and/or Incorrect Oil
A. Use engine oil that is recommended and change the engine oil at the interval that is recommended by the engines Operation and Maintenance Manual.
Maintenance intervals
Result: The engine oil was changed at the interval that is recommended by the engines Operation and Maintenance Manual.
Proceed to Test Step 2.
Result: The engine oil was not changed at the interval that is recommended by the engines Operation and Maintenance Manual.
Use at least the minimum grade of Cat oil.
Change the engine oil at the interval that is recommended. Repair or replace any damaged parts.
2. Contaminated Engine Oil
A. Obtain an S-O-S oil analysis. The analysis will contribute to a better understanding of oil contamination.
B. Check the oil filter bypass valve.
If the oil filter bypass valve is open, the oil will not be filtered. Check the oil filter bypass valve for a weak spring or for a broken spring. If the spring is broken, replace the spring. Verify that the oil bypass valve is operating correctly. Refer to the Disassembly and Assembly manual.
Refer to the Caterpillar guidelines for "Reusability and Salvage/Repair" for determining if the replacement of parts is necessary in order to perform a quality repair.
Contamination
Result: The oil is contaminated.
Determine the reason for any contamination of the engine oil and make the necessary repairs. Drain the crankcase and refill the crankcase with clean engine oil. Install new engine oil filters. Refer to the engines Operation and Maintenance Manual.
Result: The oil is not contaminated.
Proceed to Test Step 3.
3. Low Oil Pressure
A. Engine oil that is contaminated with another liquid can cause low engine oil pressure. High engine oil level can be an indication of contamination. Obtain an analysis of the engine oil.
B. The inlet screen of the suction tube for the engine oil pump can have a restriction. This restriction will cause cavitation and a loss of engine oil pressure. Check the inlet screen on the suction tube and remove any material that may be restricting engine oil flow.
When some components of the engine show wear in a short time, the cause can be a restriction in a passage for engine oil. An indicator for the engine oil pressure may indicate sufficient pressure, but a component is worn due to a lack of lubrication. In such a case, look at the passage for the engine oil supply to the component. Refer to Systems Operation/Testing and Adjusting, "Lubrication System" for additional information.
Restriction
Result: The inlet tube has a restriction.
Clear the obstruction. Verify the repair.
Result: The inlet tube does not have a restriction.
Proceed to Test Step 4.
4. Leaks in Air System
A. A leak in the air intake system may allow unfiltered air into the engine. Inspect the air intake system for streaks which may indicate a leakage of unfiltered air. Inspect all of the gaskets and the connections.
Air leak
Result: There are no air leaks.
Proceed to Test Step 5.
Result: There are air leaks.
Repair any leaks.
5. Inspect the Fuel Filters for Contamination
A. Remove the fuel filters. Inspect the fuel filters for contamination. Contaminants in the fuel such as hydrogen sulfide and sulfur can lead to the formation of acids in the crankcase. Obtain a fuel analysis.
Fuel filters
Result: The fuel has contamination.
Determine the cause of any contamination and make the necessary repairs.
Install new fuel filters. Refer to the Operation and Maintenance Manual.
Complete the procedure in the order in which the steps are listed.The procedure corrected the issue. Return the engine to service.The procedure did not correct the issue.Contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).