3116 and 3126 Marine Engines Fuel System Primary Filter (Water Separator) Element - Replace Caterpillar

Fuel System Primary Filter (Water Separator) Element - Replace
3116 and 3126 Marine Engines [SEBU6164]
1.1. Replace the Element

Water in the fuel can cause the engine to run rough. Water in the fuel may cause an electronic unit injector to fail. If the fuel has been contaminated with water, the element should be changed before the regularly scheduled interval.

The primary filter/water separator also provides filtration in order to help extend the life of the secondary fuel filter. The element should be changed regularly. If a vacuum gauge is installed, the primary filter/water separator should be changed at 50 to 70 kPa (15 to 20 inches Hg).

Replace the Element

------ WARNING! ------

Fuel leaked or spilled onto hot surfaces or electrical components can cause a fire. To help prevent possible injury, turn the start switch off when changing fuel filters or water separator elements. Clean up fuel spills immediately.


Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products.

Dispose of all fluids according to local regulations and mandates.


Do not allow dirt to enter the fuel system. Thoroughly clean the area around a fuel system component that will be disconnected. Fit a suitable cover over disconnected fuel system component.


Do not fill fuel filters with fuel before installing them. The fuel will not be filtered and could be contaminated. Contaminated fuel will cause accelerated wear to fuel system parts. The fuel system should be primed prior to starting the engine.

  1. Close the main fuel supply valve.

    Illustration 1g01453091
    (1) Element
    (2) Bowl
    (3) Drain

  2. Remove element (1) from the element mounting base while bowl (2) is attached.

  3. Dispose of the contents of the filter. Remove bowl (2) from element (1). The bowl is reusable. Do not discard the bowl. Dispose of the used element.

  4. Remove the O-ring from the gland of the bowl. Clean the following components:

    • Bowl

    • O-ring

    • Mounting base

    Inspect the O-ring for damage and for deterioration. Replace the O-ring, if necessary.

  5. Lubricate the O-ring with clean diesel fuel.

  6. Install bowl (2) on a new element. Tighten the bowl by hand. Do not use tools in order to tighten the bowl.

  7. Lubricate the top seal of element (1) with clean diesel fuel. Install the new element on the mounting base. Tighten the element by hand.


    The water separator is under suction during normal engine operation. Ensure that the vent plug is tightened securely to help prevent air from entering the fuel system.

  8. Open the main fuel supply valve.

  9. Start the engine and check for leaks. Run the engine for 1 minute. Stop the engine and check for leaks again.

    Detecting leaks is difficult while the engine is running. The primary filter/water separator is under suction. A leak will allow air to enter the fuel. The air in the fuel can cause low power due to aeration of the fuel. Ensure that the components are correctly installed to prevent air from entering the fuel system.