3176C, 3406E and 3456 Industrial Engines Troubleshooting – Oil Contains Fuel

Probable Causes

Leaking seals on the case of the unit injector or on the barrel of the unit injector
Leaking seals on the fuel line adapter for the cylinder head
Excessive leakage from the unit injector tip or breakage of the unit injector tip
Cracked fuel supply manifold
Leaking seal on the fuel transfer pump

Note: For additional information, refer to, REHS3007, “Determining the Cause of Fuel Dilution of Engine Oil”.

Recommended Actions

Leaking Seals on the Case of the Unit Injector or on the Barrel of the Unit Injector

Look for signs of damage to the seals for the unit injectors. Replace any seals that are leaking.

Leaking Seals on the Fuel Line Adapter for the Cylinder Head

Look for signs of damage to the seals on the fuel line adapter for the cylinder head. Repair any leaking fuel lines or components and/or replace any leaking fuel lines or components.

Excessive Leakage from the Unit Injector Tip or Breakage of the Unit Injector Tip

Look for signs of damage to the unit injectors. If necessary, repair the unit injectors or replace the unit injectors.

Cracked Fuel Supply Manifold

Look for signs of damage to the fuel supply manifold.

Leaking Fuel Transfer Pump Seal

Ensure that the weep hole is not plugged. If necessary, repair the fuel transfer pump or replace the fuel transfer pump.