TUBE AS 6S4728 - Caterpillar

Verifying Fuel Dilution
Always verify the fuel dilution by the combination of low oil viscosity and gas chromatograph fuel dilution test result in excess of six percent before investigating or servicing the engine. Ask your dealership to submit an oil sample to a regional Caterpillar SOS lab for analysis if a gas chromatograph fuel dilution test cannot be performed at your dealership.Troubleshooting for Sources of Fuel Dilution
Use the following procedure to determine the locations of sources of fuel dilution around the electronic unit injectors under the valve cover.The tools that are required are listed below:
1U-5566 Ultraviolet Lamp Gp
1U-5575 Additive Dye
19 L (5 US gal) container for fuelNote: The engine must be at operating temperature or near operating temperature in order to perform this test.Note: Do not exceed 745 kPa (108 psi) of fuel pressure in the rail of the cylinder head when you pressurize the fuel system with a priming pump.
Add dye to the fuel in the container per the instructions for the dye and mix well.
Put the inlet and return lines for the fuel in the container with the fuel that contains dye.
Start the engine. Operate the engine until at least 11 L (3 US gal) of fuel is used or until the fuel that contains dye has returned to the container. Stop the engine.
Remove the valve covers.
Cap the fuel line and pressurize the fuel system with a priming pump.
Use the black light to inspect all of the unit injectors. A leak is indicated by a definite streak of fuel that contains dye at the leaking location.Leaking Seals on the Body or the Sleeve of the Unit Injector
Illustration 1 g01947082
(1) Fuel leakage is normal in these areas. Do not replace the fuel injector if fuel is leaking in this area. (2) Replace the fuel injector if fuel is leaking in this area. (3) Replace the O-rings if fuel is leaking in this area. Do not replace the fuel injector.Illustration 1 shows the areas on the unit injector that leaks are normal. The Illustration also shows the areas that service may be needed.Check the torque for the unit injector clamp retaining bolts. Ensure that the unit injectors are properly installed into the cylinder head. Look for damage to the unit injector sleeves and for damage to the O-ring seals. Replace any seals or sleeves that show evidence of leakage.Leaking from the Seal from the Solenoid to the Housing or Cracked Body of the Unit Injector
Use the ""Troubleshooting for Sources of Fuel Dilution"" procedure above to confirm the location of the fuel leak either from a solenoid to the joint for the seal for the housing or from a damaged unit injector body. Remove injectors that are suspected of having a damaged body and inspect the injectors for visible cracks. Replace a unit injector if either the seal for the housing for the solenoid is leaking fuel or if the body is cracked or the body is damaged resulting in a fuel leak.Excessive Leakage from the Unit Injector Tip or a