KIT-SERVO PISTON 4425663 - Caterpillar

Introduction
This Special Instruction contains the necessary instructions for the installation of the HEUI pump compensator standby plug on 3408E and 3412E engines. In order to obtain the hydraulic pump standby pressure of 4.8 to 6.0 MPa (696 to 870 psi), nine plugs are available. The plugs are marked "A", "B", "C", "D", "E", "F", "G", "H", and "J".Procedure
Note: Previously, the plug and the screw were two separate pieces. Now, the plug and the screw are combined into one piece.
Illustration 1 g00450585
Remove the existing allen head plug and the O-ring Seal from the compensator body.
Remove the load sensing screw from the compensator body. Be careful not to remove the retaining spring, the seat, or the spool in the process.
Select the Compensator Plug that is stamped "C". Install one of the O-Ring Seals into the O-ring groove under the head of the plug.Note: One new O-ring Seal should be used on each compensator plug. Do not reuse an O-ring Seal. Reusing an O-ring Seal can lead to a bad seal.
Screw the compensator plug into the compensator until the plug is seated. Tighten the compensator plug to a torque of 25 3 N m (19 2 lb ft).
A technician must properly connect the diagnostic equipment (ET or ECAP) to the Electronic Control Module (ECM) in order to monitor the injection rail pressure.
Unplug the rail pressure control valve (RPCV). Crank the engine while you monitor the injection rail pressure. The engine may start depending on the standby injection rail pressure. If the correct compensator plug has been installed, the injection rail pressure will be 4.8 to 6.0 MPa (696 to 870 psi).
If the pressure reading is above the specified range, select the shorter Compensator Plug that is marked "D". Repeat Step 4, Step 5, and Step 6. If the pressure reading is below the specified pressure range, select the longer Compensator Plug that is marked "B". Repeat Step 4, Step 5, and Step 6. Use caution when you remove the plugs. Ensure that the retaining spring, the seat, and the spool remain in place.
If a particular compensator plug does not provide the required injection rail pressure, select the next longer plug or the next shorter plug. The longer plugs will provide higher pressure. The shorter plugs will provide lower pressure. Repeat Step 4, Step 5, and Step 6. Use this method and Table 1 in order to select a plug that will provide the required standby injection rail pressure.
Table 1
Plugs    Size    
J     Longest    
G     Longer Than "A"    
A     Longer Than "B"    
B     Longer Than "C"    
C     Nominal    
D     Shorter Than "C"    
E     Shorter Than "D"    
F     Shorter Than "E"    
H     Shortest    
Make sure that the rail pressure control valve (RPCV) is plugged in order to ensure proper operation upon completion.