SEAL 9N3131 - Caterpillar

Probable Causes
Seals
Fuel injector
Fuel transfer pump
High pressure fuel pump
Cylinder headRecommended Actions
Table 1
Troubleshooting Test Steps Values Results
1. Check for Leaking Injector O-ring Seals
A. Remove the injector from the affected cylinder and visually inspect the injector O-ring seals for damage.
B. If the leakage is not located, add the appropriate dye to the fuel tanks.
a. Run the engine at high idle for several minutes.
b. Shut down the engine and remove the valve covers.
c. Use a black light to check for traces of dye around each injector.
O-ring Seal
Result: The fuel injector O-ring seal is not damaged.
Proceed to Test Step 2.
Result: The fuel injector O-ring seal is damaged.
Repair: Replace the damaged seals.
If the problem is not resolved, proceed to Test Step 2.
2. Inspect the Fuel Injector Tip
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Use Cat ET to perform the following fuel injector test:
- "Cylinder Cutout Test"
Note: A fuel injector tip that is broken or fractured is a possible cause of a cylinder that is being overfueled.
C. If a cylinder is identified by the test, Remove the injector and check the injector tip for damage. Check the fuel injector tip for cracks or breakage.
Injector Tip
Result: The fuel injector tip is not damaged.
Proceed to Test Step 3.
Result: The fuel injector tip is damaged.
Repair: Replace damaged fuel injector. Refer to Troubleshooting, "Injector Trim File - Install" and Troubleshooting, "Injector Solenoid - Test" for additional information.
If the problem is not resolved, proceed to Test Step 3.
3. Inspect the Fuel Transfer Pump Seal
A. Check for fuel leakage around the shaft seal for the fuel transfer pump.
B. Ensure that the weep hole is not plugged.
Pump Seal
Result: There is not fuel leakage around the shaft seal.
Proceed to Test Step 4.
Result: There is fuel leakage around the shaft seal.
Repair: Replace the fuel transfer pump.
If the problem is not resolved, proceed to Test Step 4.
4. Check the High Pressure Fuel Pump
Note: Perform this test on a cold engine.
Note: Verify the "Fuel Rail Pressure" reading in ET is 0 8 MPa (1160 psi) prior to servicing the fuel system. Refer to Testing and Adjusting, "Fuel Rail Pressure - Release" for instructions on how to release the pressurized fuel.
A. Remove plug (1) from the bottom of the fuel pump. Expect engine oil will drain from the opening. Check the magnetic plug for debris.
B. Use the "Fuel Pump Relay Command Override" for the fuel priming pump to run the pump to pressurize the fuel system. Allow the pump to run for at least 5 minutes while you monitor the drain hole in the fuel pump adapter for leakage.
Note: If a manual switch is not available, use the override in Cat ET to operate the fuel priming pump. For a pump that is in good repair, fuel may drip intermittently from the adapter drain hole. The leakage must not exceed 6 mL/min (0.2 oz/min).
C. Turn the off "Fuel Pump Relay Command Override". Clean the magnetic drain plug and reinstall the drain plug into the pump.
Pump
Result: The leakage was less than 6 mL/min