Usage:
3406B, 3406C Truck Engines
Staining and fretting is sometimes found on the sealing surfaces of the fuel injection pump barrels and bonnets during pump repairs.
Staining is defined as charred or discolored fuel that is trapped in the sealing joint between the pump barrel and bonnet. See the illustration. The staining is sometimes bonded to the sealing surfaces.
Fretting is the removal of microscopic particles from the sealing face caused by very small relative movement between the sealing surfaces. Fretting may have a frosted (less shiny) surface appearance at the outer seal ring edges.
The reusability of stained or fretted bonnets or barrels can be determined by performing the following Lapping Procedure.
Lapping Procedure
NOTE: This process is intended to be more of a stain and minor fretting removal procedure, not a major remachining of the sealing faces.
1. Perform this procedure in a CLEAN area of the shop. Note: Fuel injection pump barrels and plungers are matched sets. Do not mix the components from one pump with another.
2. CLEAN the barrel and bonnet prior to lapping. If the staining is removed during cleaning, there is no need to lap the parts. Also, any staining or fretting that remains that is not in the sealing ring is acceptable. See the illustration.
Location of sealing rings. (A) is the sealing ring for a 2W-3409 Bonnet. (B) is the sealing ring for a 6I-1665 or 108-2102 Bonnet.
NOTE: If a new "Type (B)" (108-2102 or 6I-1665 Bonnet) is to be used with a barrel that previously used a "Type (A)" [2W-3409 Bonnet (full face)], the "Type (A)" bonnet sealing ring diameter is larger than the "Type (B)" bonnet sealing ring. Therefore, any barrel staining or fretting that remains outside of the "Type (B)" seal ring area is acceptable. See the illustration.
3. CLEAN hands prior to lapping.
4. Use a CLEAN sheet of 4.0 Emery Paper or 600 grit wet/dry paper mounted or attached to a CLEAN and FLAT lapping plate. This procedure will not work unless a flat plate is used.
5. With moderate downward pressure, hand lap the components with 8 to 10 figure eight strokes. If staining or fretting is still evident in the seal ring area, replace the part.
6. Do not use Emery Paper when it has a "shiny" appearance. Do not exceed ten passes on any part.
7. Visually inspect the parts. The bonnet seal ring and the barrel face should exhibit bright clean surfaces. Scratches from lapping will be visible, but they are not detrimental. Minor imperfections may be present. These imperfections are permissible unless they exceed 1/3of the sealing width. Imperfections in the "Type (B)" bonnet outside load ring are acceptable.
8. CLEAN and reassemble the good components.
NOTE: If the original bushings are reused, it is recommended that they be used in their original pump housing locations. If the original pump housing location is unknown, use a new bushing. If new bushings are used, it is recommended that "double torquing" be used to install them. Tighten the bushing to a torque of to 260 N·m (190 lb ft).
"Double torquing" is:
A. Tighten the bushing to the specified torque.
B. Then loosen the bushing 1/4to 1/2 turn.
C Then retighten the bushing to the specified torque.
Double torquing can be done with new or used bushings on any 3406B or 3406C fuel injection pump. Do not use double torquing on other fuel systems.
9. Always check the rack bar for freeness after pump installation and bushing torquing.