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SERIES 55 FUEL FILTERS (SPIN-ON)

Two spin-on type filters are used. The primary filter is mounted on the frame rail. The first in the fuel flow is a strainer, and the second is a filter. Although they are not marked as such, the threaded sleeves that accept the cartridges are different sizes to prevent mismatching. The primary filter has a 1 in. x 12 thread. The secondary filter has a 13/16 in. x 12 thread. The word "Primary" or "Secondary" is cast into the top of the respective adaptor. See Figure 24979 . ‪

1.Secondary Fuel Filter ‪

Fuel Filters

The spin-on filter cartridges consist of a shell, element, and gasket combined into a unitized replacement assembly. No separate springs or seats are required to support the filters. A fuel shutoff valve is installed on the outlet side of the secondary filter. ‪

The fuel filter adaptors are retained to the block with two bolts each. Torque these bolts to 58-73 N m (43-54 lb ft). ‪

The fuel filter system consists of the following: ‪

  • Spin-on Primary Fuel Filter
  • Primary Fuel Filter Adaptor
  • Spin-on Secondary Fuel Filter
  • Secondary Fuel Filter Adaptor
  • Fuel Shutoff Valve or Check Valve

Replacement of Fuel Filter (Spin-on)

As contaminants build up on the filter medium, a number of factors start to affect vehicle performance: ‪

  • The fuel delivery rate is reduced, making less fuel available for combustion.
  • The fuel pump is forced to work harder to move the same volume of fuel. This subjects internal seals to abnormal conditions which may lead to seal leakage. In extreme cases air can be drawn into the fuel system.
  • With the rate of flow slowed, fuel stays in the cylinder head for a longer period of time, allowing its temperature to rise above normal. Because fuel temperature has an effect on engine power, higher fuel temperatures normally result in reduced power.
  • If the restriction is severe enough, fuel vaporization can occur, resulting in pockets of air that can further reduce fuel delivery.

All of these conditions can lead to power loss and subsequent operator complaints of "low power" and "reduced vehicle fuel economy" caused by the need to downshift more frequently on grades. ‪

To determine if replacement of fuel filter (spin-on) is necessary. See Figure 21720 . ‪

Flowchart for Replacement of Fuel Filter (Spin-on)

Removal of Fuel Filter (Spin-on)

To replace the filter, perform the following step: ‪

  1. Turn off the shutoff valve.
  2. Use a suitable band wrench or filter wrench, such as J 22775 , to remove the filter(s).

Installation of Fuel Filter (Spin-on)

To install the filter, perform the following steps: ‪

  1. To install, fill the new filter replacement cartridges with clean fuel oil. Coat the gaskets slightly with clean fuel oil.

    NOTICE:

    Mechanical tightening of the fuel filters is not recommended, and may result in seal damage, cartridge damage, or both. Tighten the fuel filters by hand only. ‪

  2. Thread the new filters on the adaptor, turning them until they contact the gasket fully with no side movement of the filter evident; then turn an additional one-half turn by hand.
  3. Turn on the shutoff valve.

    Note: There is a fuel system shutoff valve on the discharge side of the secondary fuel filter. This check valve is designed to prevent loss of fuel prime at time of filter replacement.

  4. Start the engine and check for leaks.