TUBE 3111721 - Caterpillar

3406B Truck EnginesReports indicate that some dealers may be using inaccurate test procedures when troubleshooting for fuel dilution of the lube oil. In some cases, the results of the tests performed may be misinterpreted. In other cases, the most likely causes are being overlooked. When troubleshooting for fuel dilution of the lube oil, use the procedures that follow in the sequence given.
A. Verify Fuel DilutionB. Internal Fuel LinesC. Fuel Injection NozzlesD. Fuel Transfer PumpE. Fuel Injection Pump HousingVerify Fuel Dilution
Fuel dilution of the lube oil can be verified by two methods. First, by the test results of an S O S (Scheduled Oil Sampling). Second, by an increase in the oil level. If the second method is used, make sure the increase in the oil level is due to the addition of fuel.
Internal Fuel Lines
To test the internal fuel lines, it will be necessary to use the 5P4150 Nozzle Testing Group and two lengths of wire braided hose capable of withstanding a pressure of at least 20,700 kPa (3000 psi). Modify the two lengths of wire braided hose as follows:
1. Install a 6V3989 Nipple on one end of each hose. This end will be connected to the nozzle tester with a 6V4143 Coupler Assembly (Quick Disconnect).2. Weld a section of fuel line and its nut to an appropriate fitting. Install this fitting on the end of one hose.3. Weld an appropriate fitting to the bottom of a 2W3409 Fuel Pump Bonnet. Install this fitting on the end of the second hose.Check for internal leaks as follows:
1. Remove both valve covers and valve cover bases.2. Wipe off all internal fuel lines, fuel injection nozzles, and/or nozzle adapters.3. Disconnect one end of an external fuel line. Disconnect the end that is easier to work with.4. Use the appropriate hose to connect the 5P4150 Nozzle Testing Group to the external fuel line or to the fitting on the cylinder head fuel line adapter. This will make it possible to pressurize the internal fuel line and fuel injection nozzle.5. Close the on-off valve, and open the isolation valve on the tester. Pump the handle rapidly until a pressure of 20,700 kPa (3000 psi) is obtained. Close the isolation valve.6. Check for leaks at the areas shown in Illustrations 1 and 2.
Illustration 1. Location to check for internal fuel leaks with 1W2950 or 7W1902 Adapters.
Illustration 2. Locations to check for internal fuel leaks with 7W1645 Adapter.7. Do Steps 3-6 for all the cylinders.Fuel Injection Nozzles
Illustration 3. Locations to check for fuel injection nozzle leaks.To check the fuel injection nozzles for leaks, remove the nozzles from the engine. Do not remove the bleed screws. Apply a pressure of 20,700 kPa (3000 psi) to the nozzle with the 5P4150 Nozzle Testing Group. Check the nozzles for leaks in the areas shown in Illustration 3. Observe for 4 to 5 minutes. Small leaks are not readily apparent in the typical 1 to 2 minute check. It is recommended that all of the tests in Special Instruction,